unit 11: acids & bases-key regents chemistry ’14 mr ... · unit 11: acids & bases-key...

Unit 11: Acids & Bases-Key Regents Chemistry ’14-‘15 Mr. Murdoch

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Unit 11:

Acids and Bases

Student Name: ______________Key_________________

Class Period: _3, 5, & 10_



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Unit 11 Vocabulary:

1. Acidity: The property of exhibiting the qualities of an acid.

2. Alkalinity: The property of exhibiting the qualities of a base.

3. Amphiprotic: any substance (ionic or covalent) that can both accept

and donate at least one proton (H+).

4. Amphoteric: A species that can act either as a Brönsted-Lowry acid

or a Brönsted-Lowry base, depending on the other species it is

reacting with.

5. Arrhenius Acid: An electrolyte that ionizes in aqueous solution to

yield H+ as the only cation in the solution.

6. Arrhenius Base: An electrolyte that ionizes in aqueous solution to

yield OH- as the only anion in the solution.

7. Basicity: The property of exhibiting the qualities of a base.

8. Brönsted-Lowry (B-L) Acid: A species that donates H+ to a B/L base

in a chemical reaction.

9. Brönsted-Lowry (B-L) Base: A species that accepts H+ from a B/L

acid in a chemical reaction.

10. Buret: A calibrated precision (& expensive!) glass tube that

precisely measures the volume of a liquid dispensed.

11. Caustic: A substance that will destroy or irreversibly damage a

substance or surface that it contacts; usually used to describe bases.

12. Corrosive: A substance that will destroy or irreversibly damage a

substance or surface that it contacts; usually used to describe acids.

13. Electrolyte: A compound that ionizes (dissociates) in water, allowing

the solution to flow electrons freely and conduct electricity.

14. Hydrolysis: The process whereby a base reacts with a glycerol ester

(a fat) to produce soap.

15. Indicator: A substance whose color is sensitive to the pH of a

solution to which it is added.



16. Neutralization: A double-replacement reaction where an acid and a

base react to form water and a salt.

17. Nonelectrolytes: A molecular compound that does not ionize (not

dissociate) in water, preventing the solution from conducting

electricity.

18. pH: The negative logarithm of the hydrogen ion concentration. A pH

value less than 7 indicates an acidic solution, a pH value 7 is a

neutral solution, and a pH value greater than 7 indicates a basic

solution. The scale ranges from a hypothetical 0 (most acidic) to 14

(most basic).

19. Protonation: The addition of an acid’s H+ (proton) to a water

molecule to form a hydronium (H3O+) molecule.

20. Salt: An ionic compound formed when an acid and a base neutralize

each other. The salt compound consists of both the anion of the acid

and the cation of the base.

21. Titration: A process of controlled acid-base neutralization carried out

using burets dispensing either an acid or a base.



Unit 11 Homework Assignments:

Assignment: Date: Due:



Notes page:



Arrhenius Acids:

A substance that contains H+ ions that ionize when dissolved in water

is known as an Arrhenius Acid.

Acids (and bases) are the only molecules (different from ionic

crystals) that ionize (dissociate) when dissolved in water. Acids (and

bases) are electrolytes, unlike other molecular substances like water

(H2O) and sugar (C6H12O6). The H+ leaves the acid and bonds to the

water molecule to form a hydronium ion (H3O+).

Arrhenius Acid examples:

HCl(g) + H2O(l) H3O+

(aq) + Cl-(aq)

i. The acid HCl contains one H+ ion which combines with one H2O

molecule to form one H3O+

ion.

Topic: Arrhenius Acids and Bases

Objective: What is the definition of an Arrhenius Acid or Base?



ii. The acid (HCl) ionizes to form a hydrogen cation (H+) and an

anion, in this example a chloride ion (Cl-).

iii. The hydrogen ion (H+) bonds to the water molecule using a

“sneaky” bonding method. The H+ doesn’t have an electron to

share, and there are no unpaired valence electrons in the water

molecule. The hydrogen ion tends to “bogart” two electrons from

the oxygen in the water molecule. The extra hydrogen ion now has

a “claim” on the electrons on the oxygen, forming a coordinate

covalent bond.

H2SO4(l) + 2 H2O(l) 2 H3O+

(aq) + SO4-2

(aq)

iv. The acid H2SO4 contains two H+ ions which combine with two

H2O molecules to form two H3O+ hydronium ions.

H3PO4(l) + 3 H2O(l) 3 H3O+

(aq) + PO4-3

(aq)

v. The acid contains three H+ ions which combine with three H2O

molecules to form three H3O+ hydronium ions.



Properties of Acids:

Acids eat away (oxidize) active metals (metals above H2 on Table J).

Metals such as Li, Mg, and Zn may be oxidized by an acid to produce

hydrogen gas (H2(g)). These are examples of metals above H2 on

Table J. We won’t discuss metals below H2 on Table J now.

For these single replacement reactions:

2 Li(s) + 2 HCl(aq) 2 LiCl(aq) + H2(g)

Ca(s) + 2 HCl(aq) CaCl2(aq) + H2(g)

i. Both of these are examples of how a more active metal (above H2)

will “kick” the hydrogen out of the acid (HCl), leaving a new

aqueous ionic compound and hydrogen gas.

1. Acids have a pH value less than 7.

i. The pH scale measures the relative acidity or alkalinity of a

solution. A pH value 7 is neutral, and acids have a pH value less

than 7. Each decrease of one whole number of pH is a tenfold

increase in acid strength. An acid with a pH value 3 is ten times

more acidic than a solution with a pH value 4, and an acid with a

pH value 3 is 100 times more acidic than a solution with a pH

value 5.

Topic: Properties of Acids

Objective: How are ions situated within a solution?



2. Acidic solutions may conduct electricity.

i. Acids are electrolytes, because they dissociate to form ions in

solution. The stronger the acid, the more it ionizes, and therefore

could carry electron flow better and have better electrical

conductivity.

ii. Stronger electrolytes (stronger acids) include: HI, HCl, HNO3, and

H2SO4. H2SO4 is commonly used in lead-acid automotive batteries.

iii. Weaker electrolytes (weaker acids) include: H2CO3 (carbonic acid in

soda) and HC2H3O2 (acetic acid, or vinegar).

3. Dilute solutions of acids taste sour.

*NOTE: this statement does NOT give you permission

to taste ANY acid in lab to test this statement!

i. Citric acid is found in citrus fruits like lemons and grapefruits.

Citric acid is also used to give an extra sour “kick” to food and

candies.

ii. Acetic acid (5% in aqueous solution) is also known as “white

vinegar” and is yummy on salads or French Fries!



4. Acids react with carbonates to form carbon dioxide gas, a salt, and

water.

i. Baking soda and vinegar:

Spoiler Alert! - If you remember the mysterious “Enzyme M” from the required NYS Living

Environment Relationships and Biodiversity Lab, the powder was baking soda, and the 4 plant

“extract” solutions were food coloring and water, with three of the extracts containing vinegar.

NaHCO3(s) + HC2H3O2(aq) CO2(g) + H2O(l) + NaC2H3O2(aq)

This is the middle school (& VERY messy!) “volcano” reaction;

the CO2(g) forces the mixture of dry powder, liquid, and foam up

and out.

5. Acids may be formed by reaction of gaseous oxides with water.

i. Burning fossil fuels releases gaseous nonmetallic oxides (CO2,

*NOx, SO2, and similar molecules) into the atmosphere. When

these gaseous nonmetallic oxides react with atmospheric water

vapor, they form weak aqueous acids that may form acidic

precipitation. Acid precipitation can lower the pH of bodies of

water, which can seriously affect aquatic ecosystems.

*NOx is a generic symbol for the nitrogen oxides of NO, NO2, & N2O



Naming of Binary Acids:

A binary acid has a name composed of the prefix (hydro-), the

nonmetallic ion name, and the last syllable (-ide) replaced with the

suffix (-ic) followed by the separate word “acid”.

Binary Acid naming examples:

i. HCl(aq): (hydro-) + (chloride - ide) + (-ic) + “acid” = hydrochloric acid

ii. HBr(aq): (hydro-) + (bromide - ide) + (-ic) + “acid” = hydrobromic acid

iii. H2S(aq): (hydro-) + (sulfide - ide) + (-ic) + “acid” = hydrosulfic acid

iv. H3N(aq): (hydro-) + (nitride - ide) + (-ic) + “acid” = hydronitric acid

Writing of Binary Acid formulas:

i. Write a binary acid formula just like any ionic compound, placing

the H+1

first, and the anion second.

1. Hydrofluoric acid:

One hydrogen (H+1

) + one fluoride (F-1

) HF(aq)

2. Hydrophosphoric acid:

Three hydrogen (3 x H+1

) + one phosphide (P-3

) H3P(aq)

ii. Ensure that you have the correct ratio of ions to equal the charges!

Topic: Naming of Acids

Objective: How do we name acidic compounds?



Naming of Ternary Acids:

A ternary acid has a name with NO (hydro-) prefix.

a) If the polyatomic ion ends in (-ide) or (-ate), replace the last

syllable of the polyatomic ion with the suffix (-ic) followed by the

word “acid”.

b) If the polyatomic ion ends in (-ite), replace the last syllable of the

polyatomic ion with the suffix (-ous) followed by the word “acid”.

Ternary Acid naming examples:

i. HNO3(aq): (nitrate - ate) + (-ic) + “acid” nitric acid

ii. HNO2(aq): (nitrite -ite) + (-ous) + “acid” nitrous acid

iii. HClO3(aq): (chlorate - ate) + (-ic) + “acid” chloric acid

iv. HClO2(aq): (chlorite - ite) + (-ous) + “acid” chlorous acid

v. HCN(aq): (cyanide - ide) + (-ic) + “acid” cyanic acid

Writing of Ternary Acid formulas:

a) Remember that while there is no (hydro-) prefix, ternary acid

formulas still begin with hydrogen!

i. Sulfuric acid: hydrogen (2 x H+1

) + sulfate (SO4-2

) H2SO4(aq)

ii. Sulfurous acid: hydrogen (2 x H+1

) + sulfite (SO3-2

) H2SO3(aq)

a) Again, ensure that you have the correct ratio of ions to equal the

charges!



Regents Practice Questions-Acids: (Ungraded)

1. The only positive ion found in an aqueous found in a aqueous

solution of sulfuric acid is the

a) Sulfite ion

b) Sulfate ion

c) Hydroxide ion

d) Hydronium ion

2. An Arrhenius acid has

a) Only hydrogen ions in solution

b) Only hydroxide ions in solution

c) Hydrogen ions as the only positive ions in solution

d) Hydrogen ions as the only negative ions in solution

3. Which substance is an Arrhenius acid?

a) LiF(aq)

b) HBr(aq)

c) CH3CHO

d) Mg(OH)2(aq)

4. What produces hydrogen ions as the only positive ions in aqueous

solution?

a) NH3

b) HBr

c) KOH

d) NaCl

5. When HCl is dissolved in water, the only positive ion present in the

solution is the

a) Hydride ion

b) Chloride ion

c) Hydrogen ion

d) Hydroxide ion



Properties of Bases:

Bases are substances that contain aqueous hydroxide (OH-1

(aq)) ions

in solution.

1. Bases have a pH value greater than 7.

i. The pH scale measures the relative acidity or alkalinity of a

solution. A pH value 7 is neutral, and bases have a pH value

greater than 7. Each increase of one whole number of pH is a

tenfold increase in base strength. A base with a pH value 9 is ten

times more basic than a solution with a pH value 8, and a base with

a pH value 9 is 100 times more basic than a solution with a pH

value 7.

2. Basic solutions may conduct electricity.

i. Bases are electrolytes, because they dissociate to form ions in

solution. The stronger the base, the more it ionizes, and therefore

could carry electron flow better and have better conductivity.

ii. Stronger electrolytes (stronger bases) include: Group 1 metal

hydroxides (LiOH, NaOH, RbOH, and CsOH).

iii. Weaker electrolytes (weaker bases) include: Ca(OH)2, Mg(OH)2,

and Al(OH)3, all of which may be found in common antacids. We

Topic: Properties of Bases

Objective: How does temperature affect the solubility of a solution?



will learn SOON how basic antacids neutralize excess stomach

acid.

3. Bases taste bitter.

AGAIN, we will NOT test this statement in lab!

i. However, many alkaloids are found in medicines, and are also in

coffee.

ii. Theobromine is an alkaloid found in chocolate, and the compound

that makes chocolate dangerous to many pets.

4. Bases may be formed when Group 1 or Group 2 metals react with

water, releasing hydrogen gas in the process.

i. 2 Na(s) + 2 H2O(l) 2 NaOH(aq) + H2(g)

ii. Mg(s) + 2 H2O(l) Mg(OH)2 + H2(g)

5. Bases hydrolyze fats during saponification to form soap.

i. Drain cleaners usually contain sodium hydroxide which reacts

with the nonpolar molecules in grease clogging household drains.

The NaOH converts the nonpolar grease molecules into ionic soap

compounds, which then become soluble in water and may be

washed down the drain.



Naming of Bases: (Reference Table L)

1. Most common bases are formed when a metal (especially Groups 1

and 2) bonds with a hydroxide. Naming bases is easy once you've

identified them!

2. Name the metal CATION first; it keeps its name as listed in the

Periodic Table.

3. The polyatomic ion "hydroxide" (OH-) also keeps its name.

Naming of Bases examples:

i. LiOH is "lithium hydroxide"

ii. NH4OH is "ammonium hydroxide"

Topic: Naming of Bases

Objective: How do we name acidic compounds?



Regents Practice Questions-Bases: (Ungraded)

1. According to the Arrhenius theory, when a base dissolves in water it produces

a) H+ as the only positive ion in solution

b) NH4+ as the only positive ion in solution

c) OH- as the only negative ion in solution

d) CO3-2

as the only negative ion in solution

2. A sample of Ca(OH)2 is considered to be an Arrhenius base because it dissolves

in water to yield

a) H- as the only negative ions in solution

b) Ca+2

ions as the only positive ions in solution

c) OH- ions as the only negative ions in solution

d) H3O+ ions as the only positive ions in solution

3. Which ion is produced when an Arrhenius base is dissolved in water?

a) H+ as the only positive ion in solution

b) OH- ions as the only negative ion in solution

c) H3O+ ions as the only positive ion in solution

d) H- as the only negative ion in solution

4. According to the Arrhenius theory, which list of compounds includes only

bases?

a) KOH, NaOH, and LiOH

b) KOH, Ca(OH)2, and CH3OH

c) LiOH, Ca(OH)2, and C2H4(OH)2 (C2H4(OH)2 is ethylene glycol molecule)

d) NaOH, Ca(OH)2, and CH3COOH

5. According to the Arrhenius theory, when a base is dissolved in water it

produces a solution containing only one kind of anion. What is the name of this

anion?

a) Hydride ion

b) Hydroxide ion

c) Hydrogen sulfate ion

d) Hydrogen carbonate ion



Al(OH)3 is “aluminum hydroxide”

How do we know if a solution is Acidic or Basic?

Electronic pH testers:

i. Electronic pH testers have probes containing electrodes that detect

electrical conductivity. Once calibrated (a process comparing

known standards to the probe output), the electronic signal may be

interpreted to determine an ionization level, and therefore the pH

value.

Acid-Base Indicators: (Reference Table M)

i. Indicators are chemicals that have certain color characteristics for a

narrow range of pH values. Indicators may be used to determine

acidity or alkalinity, or even to find a specific range of pH values.

An indicator won’t give an exact pH value, but a range of pH

values.

Topic: Testing for pH

Objective: How do we know if a solution is Acidic or Basic?



Litmus and pH paper:

i. Red litmus paper is used to test a base. When red litmus paper is

immersed in a base, the red litmus paper turns blue indicating the

given solution as alkaline.

ii. Blue litmus paper is used to test an acid. When blue litmus paper is

immersed in an acid, the blue litmus paper turns red indicating the

given solution as acidic.



Full-range pH paper contains a mixture of indicators that will react

with a solution to give an approximation of pH value for that

solution. The color that the pH paper strip turns is compared to a

color chart for the paper that gives a quantitative pH value based on

the qualitative color.

Testing for an Acid or Base example:

An unknown solution gives the following results when tested with the

following four indicators:

Thymol Blue = yellow

Methyl Orange = yellow

Bromcresol Green = blue

Phenolphthalein = colorless

1. Which of the following pH values could the unknown solution have?

a) 2.8 b) 4.8 c) 6.5 d) 8.5



Using Reference Table M, Common Acid-Base Indicators, we

should be able to narrow down our possibilities.

i. Thymol Blue = turned yellow

Thymol Blue works between pH values of 8.0 (yellow) - 9.6

(blue). As it was yellow in this test, the unknown solution could

be at the lower end of Thymol Blue’s range, so a pH of 8.5 is a

possibility, but it also could be below a pH value 8.

ii. Methyl Orange = turned yellow

Methyl Orange works between pH values of 3.1 (red) - 4.4

(yellow). As it was yellow in this test, the unknown solution has to

be ABOVE a pH value of 3.1, so we may eliminate choice ‘A’.

iii. Bromcresol Green = turned blue

Bromcresol Green works between pH values of 3.8 (yellow) - 5.4

(blue). As it was not yellow in this test, the unknown solution has

to be ABOVE a pH value of 3.1, so we may eliminate choice ‘A’.

However, Bromcresol Green turns blue with a pH value ABOVE

5.4, so a pH of 4.8 is eliminated (along with choice ‘B’), or it

would have been green.



iv. Phenolphthalein = showed colorless (no change)

Phenolphthalein works between pH values of 8 (colorless) - 9

(pink). As it was colorless in test, the unknown solution has to be

BELOW a pH value of 8, so we may eliminate choice ‘D’.

(Geesh…I sound like a witty Sicilian…)

v. Methyl Orange eliminated a pH value 2.8, Bromcresol Green

eliminated pH value 4.8, and Phenolphthalein eliminated pH value

8.5. In this case Thymol Blue could only say that the unknown pH

was below 8, so that leaves choice ‘C’ with a pH value 6.5.



Regents Practice Questions-Indicators: (Ungraded)

1. Which solution below when mixed with a drop of bromthymol blue will

cause the indicator to change from blue to yellow?

a) 0.1 M HCl(aq)

b) 0.1 M NH3(aq)

c) 0.1 M NaOH(aq)

d) 0.1 M CH3OH(aq)

2. A solution with pH value 11 is first tested with phenolphthalein and then

with red litmus. What will be the color of each indicator in this solution?

a) Phenolphthalein is pink and red litmus is red

b) Phenolphthalein is pink and red litmus is blue

c) Phenolphthalein is colorless and red litmus is red

d) Phenolphthalein is colorless and red litmus is blue

3. The ability of H2SO4(aq) to change blue litmus paper red is mainly due to

the presence of

a) H3O+

(aq) ions

b) SO2(aq) molecules

c) SO4-2

(aq) ions

d) H2O(l) molecules

4. Pure water containing phenolphthalein will change from colorless to pink

with the addition of

a) KCl(aq)

b) HCl(aq)

c) HOH(aq)

d) KOH(aq)

5. A student records the following observations about an unknown solution:

Conducts electricity

Turns blue litmus red

The student should conclude that the unknown solution is most likely

a) A base

b) An acid

c) Normal

d) Nonpolar



Student name: _________Key________ Class Period: _3, 5, & 10_

Please carefully remove this page from your packet to hand in.

Acids & Bases Homework (1 pt. ea.)

Identify each below as an acid or base based on their formulas and properties.

Property Acid or Base Property Acid or Base

Turns litmus paper red A Turns bromthymol blue

to yellow A

Tastes sour A Tastes bitter B

Hydrolyzes fats into soap B Reacts with active

metals forming H2(g) A

HCl(aq) A KOH(aq) B

pH value 12 B Forms H3O+ in water A

Write the correct name for the following acids and bases. (Ref Table K)

1. HCl(aq): ___hydrochloric acid_________________

2. HNO3(aq): ___nitric acid_____________________

3. H2SO4(aq): ___sulfuric acid___________________

4. HC2H3O2(aq): ___acetic (or ethanoic) acid________________________

5. KOH(aq): ___potassium hydroxide_______________________

6. Ca(OH)2(aq): ___calcium hydroxide______________________



Write the correct formula for the following acids and bases. (As (aq))

7. Perchloric acid:____HClO4(aq)_______________________________

8. Hypochlorous acid: ___HClO(aq)_____________________________

9. Chromic acid: ____H2CrO4(aq)_________________________________

10. Thiosulfuric acid: ___H2S2O3(aq)__________________________

11. Aluminum hydroxide: ____Al(OH)3(aq)__________________________

12. Barium hydroxide :____Ba(OH)2(aq)__________________________

13. The results for of testing a colorless solution with three different

indicators are shown in the table below.

Indicator Result

Red litmus paper Blue

Blue litmus paper Blue

phenolphthalein Pink

Which formula could represent the solution that was tested?

a) HCl(aq)

b) NaOH(aq)

c) C6H12O6(aq)

d) C12H22O11(aq)



Neutralization:

i. The combining of an acidic (H+ donor) and basic (OH

- supplier)

forms a common molecule, HOH, or water (H2O). The anion from

the acid and the cation from the base join to form a salt. A salt is

simply an ionic compound that may be formed during acid-base

neutralization.

ii. Acid-base neutralization is a simple double-replacement reaction,

but in this case the water molecule is the precipitate. It may be

difficult to think of water as a “precipitate” WITHIN water, but in

this case the water formed is in excess.

iii. One mole of H+ ions exactly neutralizes one mole of OH

- ions.

Completing neutralization reactions:

i. Determining the products of acid-base neutralization is the SAME

process as determining the products of a double-replacement

reaction.

Watch Crash Course Chemistry Acid & Base Reactions YouTube video - 11:17

Neutralization examples:

1. HCl(aq) + NaOH(aq) NaCl(aq) + HOH(l)

Acid Base Salt Water

Topic: Acid and Base Neutralization

Objective: What occurs during acid-base neutralization reactions?

https://www.youtube.com/watch?v=ANi709MYnWg&index=8&list=PL8dPuuaLjXtPHzzYuWy6fYEaX9mQQ8oGr



2. H2SO4(aq) + 2 KOH(aq) K2SO4(aq) + 2 HOH(l)


3. 2 HNO3(aq) + Ca(OH)2(aq) Ca(NO3)2(aq) + 2 HOH(l)


Antacid neutralization:

Antacids are bases used to neutralize the acid that causes heartburn.

Almost all antacids act on excess stomach acid by neutralizing it

with weak bases. The most common of these bases are hydroxides,

carbonates, or bicarbonates.

The following table contains a list of the active ingredients found in

several common commercial antacids, and the reactions by which

these antacids neutralize the HCl in stomach acid.

Compound Formula Chemical Reaction

Aluminum

hydroxide Al(OH)3 Al(OH)3(s) + 3 HCl(aq) AlCl3(aq) + 3 H2O(l)

Calcium

carbonate CaCO3 CaCO3(s) + 2 HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)

Magnesium

carbonate MgCO3 MgCO3(s) + 2 HCl(aq) MgCl2(aq) + H2O(l) + CO2(g)

Magnesium

hydroxide Mg(OH)2 Mg(OH)2(s) + 2 HCl(aq) MgCl2(aq) + 2 H2O(l)

Sodium

bicarbonate NaHCO3 NaHCO3(aq) + HCl(aq) NaCl(aq) + H2O(l) + CO2(g)



Acid-Base Buffers:

Buffers are solutions consisting of a weak acid and its conjugate

base; these solutions resist pH changes when either acid or base is

added to it.

i. A buffered solution may contain acetic acid as its weak acid and

sodium acetate as its conjugate base. If we add some hydrochloric

acid to this solution, the sodium acetate would react with it by the

following reaction:

HCl + NaC2H3O2 ⇔ C2H3O2H + NaCl

ii. The strong HCl added to the solution has been converted to acetic

acid, a weak acid. Weak acids cause a much smaller disruption in

pH than strong acids, and the pH of the solution will decrease much

less than if it contained no sodium acetate.

iii. Likewise, if we were to add sodium hydroxide to this solution, the

acetic acid would react to it by the following process:

NaOH + C2H3O2H ⇔ NaC2H3O2 + H2O

iv. The strong base NaOH has been converted to the weak base sodium

acetate, and the pH of the solution won't rise nearly as much as if the

acetic acid weren't present in the first place.

Topic: Buffers

Objective: How may we experimentally determine concentration?



Titration:

Titration is the controlled process of acid-base neutralization that

may be used to determine the unknown molarity of an acid or base

using a precisely measured volume of a base or acid of known

molarity.

We’ll be doing a titration lab, but here are the basic steps:

1. Place a base of unknown molarity in the buret, and record the

starting volume.

2. Add phenolphthalein indicator to a measured volume of a known

molarity acid in a flask.

3. Add small quantities of the unknown molarity base to the acid until

you start to see some semi-persistent color change. The base will

cause “blooms” of bright pink in the solution when you start the

titration.

4. Once the color begins to last longer than a few moments while

gently swirling the flask, start adding the base drop-by-drop,

swirling the contents of the flask after each drop.

5. Once the flask has ANY sign of a permanent light-pink tinge,

STOP adding base, and record the ending volume in the buret.

6. For best results, do several trials. Usually the first trial is over-

titrated, and additional trials will refine your technique to get more

precise results.

Topic: Titration

Objective: How may we experimentally determine concentration?



The volume of added base (or acid if titrating acid into base instead of

base into acid) can be used along with the original volume of the acid

in the flask as well as the acid’s molarity to determine the molarity of

the unknown.

The point in the titration where the color of the phenolphthalein

indicator barely changes to a just noticeable pink is called the

ENDPOINT of the titration. Since we are adding a base to an acid,

one might think that the neutralization point would be near the

neutral pH value 7. Phenolphthalein actually changes color a little

higher on the pH scale, around pH value 8.2, a bit more basic than

neutral.

If you want to find the equivalence point, or the amount of added base

that brings the solution in the flask to exactly pH value 7, the best

way is with a pH probe. Of course, multiple trials are usually the best

way to get closest to either an endpoint or an equivalence point in a

titration.

Here is an online Titration Simulation where you can practice

working with titration calculations. Note that the “endpoint” in the

simulation occurs immediately, and is NOT the way it would work in

the lab.

http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/a_b_phtitr.html

Online Titration Simulation

Watch Crash Course Chemistry Buffers (w/ Titration) YouTube video - 11:40

http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/stoichiometry/a_b_phtitr.html

https://www.youtube.com/watch?v=8Fdt5WnYn1k



Titration Equations:

i. Remember, one mole of H+ neutralizes one mole of OH

-.

ii. Therefore, # of moles of H+ = # of moles of OH

-

iii. Since we are dealing with solutions and molarities, use the formula:

M = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒

𝐿 𝑜𝑓 𝑠𝑜𝑙𝑣𝑒𝑛𝑡

(remember this equation is “Concentration” on Reference Table T!)

iv. Rearrange the equation to:

moles = 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒

𝐿 x liters.

v. Liters are our standard unit of volume, and 𝑚𝑜𝑙𝑒𝑠 𝑜𝑓 𝑠𝑜𝑙𝑢𝑡𝑒

𝐿 is molarity

(M), so the equation becomes:

moles = M x V.

vi. Moles of acid = Macid x Vacid and moles of base = Mbase x Vbase

vii. These provide the formula:

MAcid x VAcid = MBase x VBase

viii. We can abbreviate this to:

MA x VA = MB x VB ix. A pretty simple equation to remember, but if not, it is on Reference

Table T for your use anytime as: MAVA = MBVB

x. This titration equation ONLY works if the acid used has only one H+

per acid molecule, and ONLY if the base used has only one OH- per

base molecule. We can then modify the titration equation by adding



coefficients for both the number of hydrogens in an acid (# of H) and

also the number of hydroxides in an acid (# of OH).

# H MA VA = # OH MB VB

xi. If you are only solving for moles of solute instead of molarity, the

formula may be simplified to:

# H MolesA = # OH MolesB



Titration Problem examples:

1. If it takes 15.0 mL of 0.40 M NaOH(aq) to neutralize 5.0 mL of

HCl(aq), what is the molar concentration of the HCl(aq) solution?

i. Since we are given both molarity and volume of the base, and

volume of the acid, use the equation: # H MA VA = # OH MB VB

ii. # H MA VA = # OH MB VB rearranged to solve for the molarity of

the acid is:

MA = # OH MBVB / # H VA

[(1)𝑥 (0.40 𝑀)𝑥 (15.0 𝑚𝐿)

[(1)𝑥 (5.0 𝑚𝐿) = 1.2 M HCl(aq)

2. If it takes 10.0 mL of 2.0 M H2SO4(aq) to neutralize 30.0 mL of

KOH(aq), what is the molar concentration of the KOH(aq) solution?

i. Since we are given both molarity and volume of the acid, and the

volume of the base, use the equation: # H MA VA = # OH MB VB

ii. # H MA VA = # OH MB VB rearranged to solve for molarity of the

base is:

MB = # H MAVA / # OH VB

[(2) x (2.0 M) x (10.0 mL)]

[(1) x (30.0 mL)] = 1.3 M KOH(aq)

Topic: Titration Problem Examples

Objective: How may we calculate the molarity of an unknown?



3. How many mL of 2.0 M H2SO4(aq) are required to neutralize 30.0 mL

of 1.0 M NaOH?

i. Since we are given both molarity and volume of the base, and the

molarity of the acid, use the equation: # H MA VA = # OH MB VB

ii. # H MA VA = # OH MB VB rearranged to solve for volume of the

acid is:

VA = # OH MBVB / # H MA

[(1) x (1.0 M) x (30.0 mL)]

[(2) x (2.0 M)] = 7.5 mL of 2.0 M H2SO4(aq)

4. How many mL of 0.10 M Ca(OH)2(aq) are required to neutralize 25.0

mL of 0.50 M HNO3(aq)?

i. Since we are given both molarity and volume of the acid, and the

molarity of the base, use the equation: # H MA VA = # OH MB VB

ii. # H MA VA = # OH MB VB rearranged to solve for volume of the

base is:

VB = # H MAVA / # OH MB

[(1) x (0.50 M) x (25.0 mL)]

[(2) x (0.10 M)] = 63 mL of 0.10 M Ca(OH)2(aq)



Regents Practice Questions-Titration: (Ungraded)

1. A student neutralized 16.4 mL of HCl(aq) by adding 12.7 mL of 0.620

M KOH(aq). What was the original molarity of the HCl(aq)?

a) 0.168 M

b) 0.480 M

c) 0.620 M

d) 0.801 M

2. How many mL of 0.600 M H2SO4(aq) are required to exactly neutralize

100. mL of 0.300 M Ba(OH)2(aq)?

a) 25.0 mL

b) 50.0 mL

c) 100. mL

d) 200. mL

3. The pH of a solution that is formed by the neutralization of 1.0M

H2SO4(aq) and 1.0 M KOH(aq) is closest to

a) 1 b) 4 c) 7 d) 10

4. If equal volumes of 0.1 M NaOH(aq) and 0.1 M HCl(aq) are combined,

the resulting solution will contain a salt and

a) H2O(l)

b) HCl(aq)

c) NaCl(aq)

d) NaOH(aq)

5. The following data were collected by a student performing an acid-

base titration:

Volume of aqueous acid (HCl) used: 20.0 mL

Molarity of aqueous acid (HCl) used: 0.50 M

Volume of aqueous base (NaOH) used: 40.0 mL

From the collected data, the concentration of the base should be

calculated as

a) 1.0 M b) 2.0 M c) 0.25 M d) 0.50 M



Student name: _________________________ Class Period: _______


Acid and Base Neutralization Homework

Write the formula of the salt formed from each reaction below. (1 pt. ea.)

1. H2SO4(aq) + Mg(OH)2(aq) 2 H2O(l) + _____MgSO4____ (aq)

2. H2CO3(aq) + 2 KOH(aq) 2 H2O (l) + ______K2CO3____ (aq)

Write the formula of the unknown used in each reaction and balance. (4 pts. ea.)

3. ____3 H2SO4____(aq) + _2_ Al(OH)3(aq) _6_ H2O (l) + ___ Al2(SO4)3(aq)

4. _2_ HCl(aq) + _________Ca(OH)2_________(aq) ___ CaCl2(aq) + _2_ H2O(l)

Solve the following titration problems, showing ALL steps. (2 pts. ea.)

5. How many moles of KOH(aq) are needed to completely neutralize 1.5 moles of

H2SO4(aq)?

Cont’d on back:



6. What volume of 5.0 M NaOH(aq) is needed to neutralize 40. mL of 2.0 M

HCl(aq)?

7. What is the molarity of a NaOH(aq) solution if it takes 100. mL of a NaOH to

completely neutralize 50. mL of 0.10 M H2SO4(aq)?



37 g of NaCl x 3.55 = 131.55, or about 130 grams of NaCl are soluble in

355 grams of water at 10°C

Power of Hydronium Ion in a Solution:

The unit pH is a measure of the hydrogen ion concentration in an

aqueous solution. (paired [ ] means concentration)

i. Pure water is in equilibrium (remember that?) where a small

amount of water molecules dissociate from HOH to form H+ and

OH- ions.

ii. H2O H+ + OH

-, and then the free H

+ form a coordinate bond

with another H2O molecule to form a H3O+ hydronium ion.

iii. This is a SMALL number; in neutral water, the concentration of H+

= 1.0 x 10-7

M, so the pH of pure water is given as 7.

Topic: pH

Objective: What do we mean by the expression of pH?



Adding Acids to Water:

When adding an acid to pure water, the added acid increases the

H3O+ concentration, so that the pH increases by one with each tenfold

increase in acid strength. (paired [ ] means concentration)

i. If the concentration of H3O+ = 10

-1 M, the pH value is 1 (absolute

value of the exponent equals the pH value for an acid)

ii. If the concentration of H3O+ = 10

-3 M, the pH value is 3

iii. If the concentration of H3O+ = 10


iv. If the concentration of H3O+ = 10


v. If the concentration of H3O+ = 5 x 10

-6 M, the pH value is 6.5

vi. If the concentration of H3O+ = 2 x 10


vii. A solution with a pH value 3 is tenfold more acidic than a solution

with a pH value 4.

viii. A solution with a pH value 3 is a thousand fold more acidic than a

solution with a pH value 6.

ix. A solution with a pH value 4.4 is four times more acidic than a


x. A solution with a pH value 4.7 is seven times more acidic than a


Topic: Adding Acids to Water

Objective: What happens to pH when we add an acid to water?



Adding Bases to Water:

When adding a base to pure water, the added base increases the OH-

concentration, so that the pH increases by one with each tenfold

increase in base strength. (paired [ ] means concentration)

i. If the concentration of OH- = 10

-1 M, the pH value is 13 (value of the

exponent subtracted from 14 equals the pH value for an base)

ii. If the concentration of OH- = 10


iii. If the concentration of OH- = 10


iv. If the concentration of OH- = 5 x 10


v. If the concentration of OH- = 7 x 10


vi. A solution with a pH value 9 is tenfold more basic than a solution

with a pH value 8.

vii. A solution with a pH value 11 is a thousand fold more basic than a


viii. A solution with a pH value 8.8 is eight times more basic than a


ix. A solution with a pH value 11.2 is two times more basic than a


Topic: Adding Bases to Water

Objective: What happens to pH when we add a base to water?



Comparing Common examples of pH values:

Watch Bozeman Chemistry Acids, Bases, & pH YouTube video - 8:53

https://www.youtube.com/watch?v=Xeuyc55LqiY



Regents Practice Questions-pH: (Ungraded)

1. Which statement below correctly describes a solution with a pH of 9?

a) It has a higher concentration of H3O+ than OH

- and causes red litmus paper

to turn blue

b) It has a higher concentration of OH- than H3O

+ and causes red litmus

paper to turn blue

c) It has a higher concentration of OH- than H3O

+ and causes methyl orange to

turn red

d) It has a higher concentration of H3O+ than OH

- and causes methyl orange to

turn yellow

2. Which pH change represents a hundredfold (100x) increase in the concentration of

H3O+?

a) pH 3 to pH 1

b) pH 4 to pH 3

c) pH 5 to pH 7

d) pH 13 to pH 14

3. Given the following solutions:

i. Solution A: pH of 5

ii. Solution B: pH of 7

iii. Solution C: pH of 10

Which list below has the solutions placed in order of increasing H+

concentration?

a) A B C

b) C A B

c) B A C

d) C B A

4. Which relationship is present in a solution with a pH of 7?

a) [H+] = [OH

-]

b) [H+] > [OH

-]

c) [H+] < [OH

-]

d) [H+] + [OH

-] = 7

5. What is the H3O+ ion concentration of a solution that has an OH

- ion concentration

of 1.0 x 10-3

M?

a) 1.0 x 10-3

M

b) 1.0 x 10-7

M

c) 1.0 x 10-11

M

d) 1.0 x 10-14

M



Notes page:





pH Homework

Circle the correct answer for each multiple choice question. (1 pt. ea.)

1. Which of the following pH values is the most acidic?

a) 5 b) 7 c) 9 d) 11

2. Which of the following pH values is the most basic?

a) 5 b) 7 c) 9 d) 11

3. Which of the following 1 x 10-5

M in aqueous solution could have a pH of 5?

a) CH4 b) HCl c) NaCl d) NaOH

4. What would be the pH of a solution of made from equal volumes of 0.1 M

HCl(aq) and 0.1 M NaOH(aq)?

a) 0.2

b) Exactly 7

c) Less than 7

d) Greater than 7

5. Which pH value would indicate a solution as the better acidic electrolyte?

a) 3 b) 5 c) 9 d) 12

6. Which pH value would indicate a solution as the poorer basic electrolyte?

a) 3 b) 5 c) 9 d) 12

Short answer questions. (1 pt. ea.)

7. A pH of 4 is how many times more acidic than a pH of 6? __100 x__

8. A pH of 11 is how many times more acidic than a pH of 8? __0.001 x__

9. Neutral pH is how many times more acidic than a pH of 2? __0.00001 x__



Brönsted-Lowry Acids and Bases:

The discussion we have had so far is concerning the Svante Arrhenius

theory on what makes an acid and acid, and a base a base. Two other

scientists, Johannes Brönsted and Thomas Lowry published separate

(but almost simultaneously) alternative theories about a more general

theory of acids and bases. For the Brönsted-Lowry theory of acids and

bases, a specific subset of what Brönsted-Lowry call acids and bases

include the Arrhenius acids and bases, so the Arrhenius classification is

more restrictive as what makes an acid or a base than the Brönsted-

Lowry classification.

Topic: Brönsted-Lowry Acids & Bases

Objective: Describe acids and bases using only H+ ions.



1. According to Arrhenius:

i. Arrhenius Acid: A compound that dissociates in water to produce H+

that is the ONLY positive cation in the solution.

ii. Arrhenius Base: A compound that dissociates in water to produce

OH- as the ONLY negative anion in the solution.

2. According to Brönsted-Lowry:

i. Brönsted-Lowry Acid: Any substance that donates a proton (H+).

a) A neutral hydrogen atom (11H

0) has only one proton and one

electron to start with. Remove the e-, and all you have is the

proton, which we write as H+. The Brönsted-Lowry theory states

any substance that gives a H+ cation (a proton) is therefore a

Brönsted-Lowry acid.

ii. Brönsted-Lowry Base: Any substance that accepts a proton (H+).

b) The Brönsted-Lowry theory states any substance that accepts a H+

cation (a proton) is therefore a Brönsted-Lowry base.

Watch The Fuse School Bronsted-Lowry Theory video - 3:55

Topic: Comparing Acid-Base Theory

Objective: How do Arrhenius and Brönsted-Lowry theories compare?

https://www.youtube.com/watch?v=ZiokqP0aZ1E



Brönsted-Lowry theory examples:

1. HCl(g) + H2O(l) H3O+1

(aq) + Cl-1

(aq)

Acid Base

a) The HCl donated its H+ to the H2O forming H3O

+

b) As HCl lost (donated) an H+, it is the Brönsted-Lowry acid. As

H2O gained (accepted) the H+, it is the Brönsted-Lowry base.

2. NH3(g) + H2O(l) NH4+1

(aq) + OH-1

Base Acid

a) The H2O donated an H+ to the NH3 forming NH4

+

b) As H2O lost (donated) an H+, it is the Brönsted-Lowry acid. As

NH3 gained (accepted) the H+, it is the Brönsted-Lowry base.

Yup…water may act as both acid and base. Fun, eh?



3. HC2H3O2(aq) + H2O(l) H3O+1

(aq) + C2H3O2-1

(aq)

Acid Base

a) The HC2H3O2(aq) donated an H+ to the H2O

b) As HC2H3O2 lost (donated) an H+, it is the Brönsted-Lowry acid.

As H2O gained (accepted) the H+, it is the Brönsted-Lowry base.



Regents Practice - Brönsted-Lowry Acids and Bases: (Ungraded)

1. Given the reaction of NH3(g) + H2O(l) NH4+

(aq) + OH-(aq):

Water acts in this reaction as the

a) Acid

b) Base

c) Electron donor

d) Proton acceptor

2. According to the “alternative theory” of acids and bases, an acid is

any species that

a) Releases oxide ions into solution

b) Donates protons to another species

c) Releases hydroxide ions into solution

d) Accepts protons from another species

3. In the reaction NH3 + HCl NH4+1

+ Cl-1

:

The NH3 acts in this reaction as

a) A Brönsted-Lowry acid, only

b) A Brönsted-Lowry base, only

c) Both a Brönsted-Lowry acid and a Brönsted-Lowry base

d) Neither a Brönsted-Lowry acid nor a Brönsted-Lowry base

4. In which forward reaction below is water acting only as a proton

acceptor?

a) H2O(l) + H2O(l) H3O+

(aq) + OH-(aq)

b) NH3(g) + H2O(l) NH4+

(aq) + OH-(aq)

c) H2SO4(aq) + H2O(l) HSO4-1

(aq) + H3O+1

(aq)

d) CH3COO-1

(aq) + H2O(l) CH3COOH(aq) + OH-(aq)



Notes page:





Brönsted-Lowry Acids and Bases Homework

For each of the following equilibrium systems, identify the Brönsted-Lowry acid

and the Brönsted-Lowry base on the reactant side. Place a capital “A” over the

Brönsted-Lowry acid, and a capital “B” over the base.

A B

1. HBr + H2O H3O+ + Br-

B A *Note that HERE one water acts as a base; the other water acts as an acid

2. H2O + H2O H3O+ + OH-

A B

3. NH3 + OH- NH2- + H2O

B A

4. H2O + HPO4-2 PO4

-3 + H3O+

A B

5. H3PO4 + H2O H2PO4- + H3O

+

B A

6. CH3COO- + H3O+ HCH3COO + H2O

A B

7. H2PO4- + CH3COO-

HCH3COO + HPO4-2

A B

8. H2O + S-2 HS- + OH-

B A

9. CN- + HCH3COO HCN + CH3COO-

B A

10. OH- + NH4+ H2O + NH3



Notes page:

unit 11: acids & bases-key regents chemistry ’14 mr ... · unit 11: acids & bases-key...

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