Name___________________________ Per. _____

Notes: Acids and Bases (text Ch. 14 & 15)

NOTE: This set of class notes is not complete. We will be filling in information in class. If you are absent, it is your responsibility to get missing information from a fellow classmate or the chemistry website: http://othschem.weebly.com/ I. Properties of Acids and Bases Acids Bases Contain more H+ than OH- ions Contain more OH- than H+ ions pH less than 7 (acidic) pH greater than 7 (alkaline) Taste sour Taste bitter, feel slippery Turn litmus red Turn litmus blue Conduct electricity (are electrolytes) Conduct electricity (are electrolytes) React with metals to produce hydrogen gas React with acids to produce a salt and water Examples of common household acids and bases: • Acids: lemon juice and other citrus juices (citric acid, ascorbic acid), tomato juice (ascorbic acid),

vinegar (acetic acid), carbonated beverages (carbonic acid) • Bases: ammonia (NH3), drain cleaner (NaOH or lye), antacids (CaCO3), bleach (NaClO), baking

soda (NaHCO3), and soaps/shampoos II. Acid-Base Theories Theory Acid defined as: Base defined as: Examples Arrhenius

Bronsted-Lowry*

*The Bronsted-Lowry theory includes the terminology conjugate acid and conjugate base. • Conjugate acid is the particle formed when a base has accepted a proton (H+).

Every base has a conjugate acid. • Conjugate base is the particle formed when an acid has donated a proton (H+).

Every acid has a conjugate base. A conjugate acid-base pair are the 2 substances related by loss or gain of a single hydrogen ion.

Identify the acid, base, conjugate acid, and conjugate base in the following reaction:

HCl + H2O →← H3O+ + Cl –

NH3 + H2O →← NH4 + + OH –

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III. Review: Nomenclature of Acids & Bases • Writing acid names from formulas: Acids are composed of hydrogen (H+) followed by an anion (negative ion). If the acid formula contains oxygen in the anion, such as in H2SO4, it is known as an oxyacid. 3 rules, based on the anion name: 1) H + anion ending in –ide: Acid name is “hydro_____ic acid” Take the root from the anion name and fill in the blank. Examples: HCl Cl- is the anion, its name is chloride Name of acid is: hydrochloric acid HF F- is the anion, its name is fluoride Name of acid is: hydrofluoric acid 2) H + anion ending in –ate: Acid name is “_____ic acid” Take the root from the anion name and fill in the blank. “What I ATE was ICky” Examples: HNO3 NO3 1- is the anion, its name is nitrate Name of acid is: nitric acid H2CO3 CO3 2- is the anion, its name is carbonate Name of acid is: carbonic acid Note: when the anion contains sulfur or phosphorus, the roots are sulfur- and phosphor-, respectively, not sulf- and phosph-. So H2SO4 is sulfuric acid, not sulfic acid. And H3PO4 is phosphoric acid, not phosphic acid. 3) H + anion ending in –ite: Acid name is “_____ous acid” Take the root from the anion name and fill in the blank. “The snake bITE was poisonOUS” Examples: HNO2 NO2 1- is the anion, its name is nitrite Name of acid is: nitrous acid HClO2 ClO2 1- is the anion, its name is chlorite Name of acid is: chlorous acid • Writing acid formulas from names: Sometimes you may be asked to write the formula for the acid, given the name. In this case you would just work backwards, using the 3 rules above. Acid formulas must be criss-crossed, as we learned with ionic compounds, so that the charges equal out to zero. Examples: Hydrobromic acid anion is bromide (Br -) formula is HBr

Acetic acid anion is acetate (C2H3O2 -) formula is HC2H3O2

Phosphorous acid anion is phosphite (PO3 3-) formula is H3PO3

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• Writing base names from formulas: There are many substances that act as bases in chemistry, with various formulas. But we are only going to focus on the hydroxides, and also ammonia. Hydroxide bases are composed of a cation (positive ion) followed by hydroxide (OH-). Naming bases is much simpler than naming acids. Name the cation and then add “hydroxide.” Examples: NaOH name of base: sodium hydroxide Mg(OH)2 name of base: magnesium hydroxide Memorize: NH3 = ammonia LiOH name of base: lithium hydroxide • Writing base formulas from names: Writing base formulas is straightforward. Find the formula for the cation and then add OH -. You also need to criss-cross the formula so that the charges equal out to zero. Examples: potassium hydroxide cation is potassium (K+) formula is KOH calcium hydroxide cation is calcium (Ca 2+) formula is Ca(OH)2

aluminum hydroxide cation is aluminum (Al 3+) formula is Al(OH)3 IV. Strong/Weak Acids and Bases Strong acids and bases ionize completely in aqueous solution to produce free H+ or free OH- ions. Free H+ and OH- give acids and bases their power. Any substance that ionizes or dissociates completely or almost completely in aqueous solution is known as an electrolyte. Solutions of electrolytes conduct electricity. Strong electrolytes are strong acids, strong bases, and soluble salts. Strong acids Strong bases HCl Group I and II soluble hydroxides, such as: HBr NaOH HI Ca(OH)2 HIO4 HClO4 HClO3 HNO3 H2SO4 ***Acids and bases not on these lists are weak, meaning they ionize only a small amount. They are also weak electrolytes. • Concentrated and dilute vs. Strong and weak Concentrated solutions have a large amount of dissolved solute and a Molarity > 1. Dilute solutions have a small amount of dissolved solute and a Molarity ≤ 1. This is independent of the extent of ionization which determines if the acid or base is strong or weak. Examples: 1 M HCl strong and dilute 12 M HCl strong and concentrated

1 M H2CO3 weak and dilute 16 M H2CO3 weak and concentrated

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V. The pH Scale pH is a numerical scale, typically ranging from 0-14. pH stands for “power of hydrogen ion.” Diagram of the pH scale: pH gives us a quantitative measure of the acidity or basicity of the aqueous solution. Whether or not a solution is acidic, basic, or neutral depends on the balance of H+ and OH- ions:

Neutral: [H+] = [OH-] Acid: [H+] > [OH-] Base: [H+] < [OH-]

The concentrations of these ions are usually very small numbers, like 1.0 x 10 – 8 M, so the pH scale was developed to generate numbers that are easier to work with. VI. pH Calculations • pH is the negative base 10 logarithm of the hydrogen ion concentration: pH = - log10 [H+] Review of base 10 logs: [H+] = 1.0 x 10 -3 What is the base 10 log? What is the negative base 10 log (the pH)? [H+] = 1.0 x 10 - 4 What is the base 10 log? What is the negative base 10 log (the pH)? ***Notice that if the [H+] decreases by a factor of 10 (1 decimal place to left), the pH goes up by 1. • We can also calculate pOH: pOH = - log10 [OH-]. pH is just used more often than pOH. There is a special relationship between pH and pOH. • Because [H+] x [OH-] = 1.0 x 10 -14, this means that pH + pOH = 14.

pH pOH Solution type H+ concentration OH- concentration = 7 = 7 Neutral 1.0 x 10 -7 1.0 x 10 -7 < 7 > 7 Acidic > 1.0 x 10 -7 < 1.0 x 10 -7 > 7 < 7 Basic < 1.0 x 10 -7 > 1.0 x 10 -7

***For practice, do worksheet on pH calculations*** Use “Guide to pH Calculations” (last page of notes) to help you.

VII. Neutralization Reactions Neutralization reactions are double replacement reactions between an acid and a base:

acid + base salt (ionic compound) + water Examples: 1. HCl (aq) + NaOH (aq) 2. H2SO4 (aq) + KOH (aq) 3. HNO3 (aq) + Ca(OH)2 (aq)

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VIII. Titrations A titration is a laboratory procedure in which an acid of unknown Molarity (concentration) is mixed with a base of known Molarity (concentration) until neutralization occurs. By measuring the volumes of acid and base necessary for neutralization to occur, the concentration of the unknown can be calculated. This is the purpose of a titration. Laboratory Setup: A buret is used to dispense the base in a precise manner, in order to combine it with the acid. An indicator, such as phenolphthalein, bromthymol blue, or methyl red, is a chemical that is used to identify (through a color change) when neutralization has occurred. Without an indicator, you cannot tell when neutralization occurs. The point at which the acid and base stoichiometry is equal (there is one mole of acid for every one mole of base) is the equivalence point. We say that neutralization has occurred here. The point at which the indicator changes color is called the end point. We must choose our indicator so that the end point and equivalence point coincide as closely as possible. Different combinations of acid and base require different indicators for a successful titration. Discussion of how to choose the indicator is beyond the scope of this course. Titration calculations: ***First you need a balanced neutralization equation*** This formula can be used to solve all titration problems:

nb Ma Va = na Mb Vb nb = coefficient of base in bal. eqn. na = coefficient of acid in bal. eqn. Ma = molarity of acid Mb = molarity of base Va = volume of acid Vb = volume of base Examples: 1. What is the molarity of a HCl solution if 55.0 mL neutralized 75.0 mL of 2.0 M NaOH? Equation:_____________________________________________________________________ 2. What is the molarity of a Ca(OH)2 solution if 20.0 mL neutralized 5.0 mL of 1.0 M HNO3? Equation:_____________________________________________________________________

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GUIDE TO pH CALCULATIONS

1. Given pH, find pOH

Remember that pH + pOH = 14 Examples:

a. pH = 7 pOH= b. pH = 3 pOH=

2. Given pOH, find pH

Remember that pH + pOH = 14 Examples:

c. pOH = 10 pH= d. pOH = 0 pH=

3. Given [H+], find [OH-]

Remember that [H+] x [OH-] = 1.0 x 10-14

Examples: e. [H+] = 1.0 x 10-9 [OH-] = f. [H+] = 1.0 x 10-2 [OH-] =

4. Given [OH-], find [H+]

Remember that [H+] x [OH-] = 1.0 x 10-14

Examples: g. [OH-] = 1.0 x 10-6 [H+] = h. [OH-] = 7.3 x 10-12 [H+] =

5. Given [H+], find pH:

Take the negative base 10 logarithm of [H+]

On the calculator press: - ctrl 10x to put in: -log[H+] Examples:

i. [H+] = 1.0 x 10-7 pH= j. [H+] = 3.5 x 10-10 pH=

6. Given [OH-], find pOH:

Take the negative base 10 logarithm of [OH-]

On the calculator press: - ctrl 10x to put in: -log[OH-] Examples:

k. [OH-] = 1.0 x 10-3 pOH = l. [OH-] = 2.5 x 10-13 pOH =

7. Given pH, find [H+]:

Find 10 ^ - pH (on the calculator, press 10x and type in - pH) Examples:

m. pH = 3 [H+] = n. pH = 10.5 [H+] =

8. Given pOH, find [OH-]:

Find 10 ^ - pOH (on the calculator, press 10x and type in - pOH) Examples:

o. pOH = 9 [OH-] = p. pOH = 5.2 [OH-] =

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