elements, mixtures and · web viewit is not just copper(ii) oxide and zinc oxide that have ......

Lesmahagow High School Acids and Bases

Lesmahagow High SchoolS4 Chemistry

Acids and BasesThe effect of soluble oxides on the pH of water and their environmental impact - Acid Rain. National 4

The uses of acids on food and drink and their impact on health.National 4

Dissociation of water into H+ and OH- ions and the excess of these ions producing acids or alkalis respectively.National 5

Neutralisation of acids with alkalis produces salts which can be named from the reactants used.National 4

Titration can be used to analyse acids or alkalis of unknown concentration by reacting them with known concentrations of a neutraliser.National 5

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Learning Outcomes – Acids and BasesCircle a face to show how much understanding you have of each statement: if you fully understand enough to do what the outcome says, if you have some understanding of the statement, and if you do not yet understand enough to do what the statement says. Once you have completed this, you will be able to tell which parts of the topic that you need to revise, by either looking at your notes again or by asking for an explanation from your teacher or classmates.

National 4 Learning OutcomesBy the end of this topic I will be able to:

1. Describe practical activities to compare the properties of acids and bases.

2. Demonstrate ways of measuring and adjusting pH.

3. Describe the significance of pH in everyday lifee.g in soils, insect stings, toothpaste, indigestionremedies, foods etc.

4. Participate in practical activities to evaluate the effect of dilution on pH values.

5. State that acids are produced from soluble non-metal oxides when they are dissolved in water.

6. State that alkalis are produced from soluble metaloxides. Insoluble metals oxides and carbonates arebases.

7. Give examples of the uses of acids and alkalis in everyday foodstuffs.

8. State that reactions like neutralisation, where heat isgiven out, are known as EXOTHERMIC reactions.

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National 5 Learning Outcomes

9. State that an acid solution contains more H+ions than pure water

10. State that an alkaline solution contains more OH-ionsthan pure water

11. Explain the effect of dilution on the pH of an acid or alkali in terms of the decreasing concentration of hydrogen and hydroxide ions.

12. State that in water and neutral solutions, the concentration of hydrogen ions is equal to the concentration of hydroxide ions.

13. Write the equation for water dissociating into H+

and OH- ions.

14. Use the dissociation of water to explain how acidsand alkalis form.

15. Use titration calculations to determine the unknown concentration of an acid or alkali.

16. State that insoluble salts formed in a neutralisation are a type of precipitate.

17. Identify the spectator ions in a neutralisation or precipitation reaction.

18. Identify the products formed when an acid is neutralisedby different bases.

19. Name the salts formed from a given acid and alkali.

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Acids and Bases Notes

National 4 Notes

Acids and Alkalis (Revision)

You will have come across acids in the lab, e.g. hydrochloric acid, sulphuric acid and nitric acid. These bottles are labelled with the warning symbol for 'irritant'. Any spills must be washed off with water … if you don’t do this, your skin will soon feel itchy. We often say that an acid ‘burns’ the skin but this is not the same as what happens when a fuel burns!

Alkalis are also found in the lab, e.g. sodium hydroxide solution. Like acids, the bottles are labelled with the warning symbol for 'irritant'. Alkalis feel soapy if spilled on your skin.

Acids are all around us in many ‘things’ that we take for granted, even in foods and our bodies … so not all acids are dangerous! The same applies to alkalis. From your S3 work, you should be able to list some laboratory acids/alkalis and some household acids/alkalis.

The pH Scale and Solutions

Universal indicator and pH paper can be used to identify solutions as being acid or alkali. They can also be used to ‘measure’ just how much acid or aqueous alkali is in a solution.

The scale that is used is called the pH scale. This is a continuous scale that runs from below 0 (acid) to above 14 (alkali) with water and neutral solutions having a pH of 7. Acidity and alkalinity increase as the pH moves away from 7, i.e. the lower the pH of a solution (below 7), the greater the acidity and the higher the pH of a solution (above 7), the greater the alkalinity.

Universal indicator can only measure the pH to the nearest whole number. A pH meter can be used to give a more accurate measurement of acidity and alkalinity.

The indicator turns a different colour at each pH number and so the pH of acids and alkalis can be found by colour-matching with a chart.

Red Orange / Yellow Green Green/blue Blue/Purple

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Remember that the pH of a substance can only be measured in aqueous solution - any solids must be dissolved first. A solution is formed when a substance dissolves in water.

Concentrated and Dilute

A concentrated solution has a lot of the dissolved substance in a certain volume of water …. think of concentrated orange juice. Adding water dilutes the solution.

If we compare the same volume of a concentrated and dilute solution, the dilute solution will have less dissolved substance than the concentrated solution.

In the same way, adding water to an acid or an alkali dilutes the solution. This affects both the acidity/alkalinity and the pH of the solutions.

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concentratedsolution

dilutesolution

dilution

ACID ALKALI

more dilute aciddecreasing acidity

increasing pH

NEUTRAL

more dilute alkalidecreasing alkalinity

decreasing pH

1 mole of methane molecules12 + (1x4)CH4

1 mole of magnesium oxide24 + 16MgO

1 mole of hydrogen molecules1x2H2

1 mole of nitric acid1+14+(3x16)HNO3

ContainsFormula MassSymbol


Note that diluting a solution by a factor of 10 (e.g. 1ml of solution diluted with water up to 10ml) will only change its pH value by 1. In other words a pH 2 solution is TEN times more acidic than a pH 3 solution.

Calculating Concentration of Solutions

The concentration of a chemical is measured in mol/l and tells us exactly how many moles of a solute is dissolved in 1 litre of solution, but how is this calculated?

Firstly, chemists need to use a measurement called the mole to help calculate this. The mole is a chemist’s way of measuring the amount of a substance. The formula mass in grams of any substance contains the same number of particles and is known as the mole.

If we know the exact concentration of a solution it is called a ‘standard solution’.

A solution labelled 1 mol l-1 contains one mole of substance dissolved in one litre of solution.

A solution labelled 2 mol l-1 contains two moles of substance dissolved in one litre of solution.

Example 1: How many moles are there in 100 cm3 of sodium hydroxide solution, concentration 0.4 mol l-1?

0.4 mol l-1 is 0.4 mol in a litre

1000 cm3 0.4 mol

100 cm3 0.04 mol

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Example 2: What is the concentration of a solution of hydrochloric acid containing 0.1 mol in 50 cm3?

50 cm3 0.1 mol

1000 cm3 0.1 x 1000 50

concentration is 2 mol l-1

Example 3: What volume of a sodium carbonate solution, concentration 2 mol l-1, contains 0.5 mol?

2 mol l-1 is 2 mol in a litre

2 mol 1000 cm3

0.5 mol 1000 x 0.5 2

There is also a short way of calculating concentration, by rearranging the equation given below:

n = CV so C = n/V

Remember the answer you get will be in litres.Acids from Non-Metal Oxides

An element that reacts with oxygen forms an oxide. Carbon, nitrogen and sulphur are all non-metals. Carbon forms carbon dioxide (CO2), nitrogen forms nitrogen dioxide (NO2) and sulphur forms sulphur dioxide (SO2).

What is the effect of carbon dioxide, nitrogen dioxide and sulphur dioxide on the pH of water?

It is not just the oxides of carbon, nitrogen and sulphur that lower the pH of water … all non-metal oxides that dissolve in water form acidic solutions.

Sulphur dioxide is produced in the atmosphere by the burning of sulphur, either as the element or as part of a compound. Nitrogen dioxide is released into the atmosphere in car exhaust fumes. Both gases dissolve in water to form acid rain. The cost of finding solutions to the acid rain problem has to be weighed against the cost of long-term damage to the world around us. Check your S3 notes for more info on acid rain.

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= 2 mol

= 250 cm3


What is an acid?

Hydrochloric acid, sulphuric acid and nitric acid are common acids.

The chemical formulae for the three acids show symbols for non-metal elements and this suggests that the acids are made up of molecules. However, dilute acids conduct electricity. This means that ions (charged particles) exist in the solutions.

During electrolysis, hydrogen gas is produced at the negative electrode. This means that the hydrogen in an acid must exist as positive hydrogen ions, H+

(aq). At the negative electrode, the hydrogen ions, 2H+ (aq), gain electrons to form uncharged hydrogen molecules.

2H+ (aq) + 2e- H2 (g)

It is the presence of aqueous hydrogen ions, H + (aq), that makes a solution an acid.

The term ‘acid’ is also used for compounds that dissolve in water to produce H+

(aq) ions, e.g. solid formic acid and hydrogen chloride gas.

HCl (g) + H2O HCl (aq) [H+ (aq) + Cl- (aq)] hydrogen chloride hydrochloric acid

HCOOH (s) + H2O HCOOH (aq) [H+ (aq) + HCOO- (aq)] hydrogen formate formic acid

The substance added is made up of molecules. When the substance dissolves in water, the covalent bonds beak to form ions that become attached to water molecules, i.e. H+ (aq) ions.

Alkalis from Metal OxidesWhen a metal reacts with oxygen, the metal oxide is formed, e.g. sodium produces sodium oxide, calcium produces calcium oxide.

Some metal oxides are soluble in water, e.g. sodium oxide and barium oxide.

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hydrochloric

acid

HCl (aq)

sulphuric

acid

H2SO4 (aq)

nitric

acid

HNO3 (aq)


What is the effect of sodium oxide and barium oxide on the pH of water?

It is not just the oxides of sodium and barium that increase the pH of water … all metal oxides that dissolve in water form alkaline solutions.

Some metal oxides are insoluble in water, e.g. copper(II) oxide and zinc oxide.

What is the effect of copper(II) oxide and zinc oxide on the pH of water?

It is not just copper(II) oxide and zinc oxide that have no effect on the pH of water … all metal oxides that are insoluble in water behave in this way.

The solubility of selected metal oxides is shown on page … of the Data Booklet. Only oxides with the letter ‘i’ are sufficiently insoluble to have no effect on the pH of water.

Place each of the following metal oxides in the correct column in the table below.potassium oxide, nickel oxide, lithium oxide, tin(II) oxide, calcium oxide, iron(III) oxide

Dissolves to form an alkali No effect on the pH of water

What is an alkali? Each of the three solutions shown is an alkali. All three conduct electricity showing the presence of ions.

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sodiumhydroxide

NaOH (aq)

potassiumhydroxide

KOH (aq)

ammoniumhydroxide

NH4OH (aq)


The names and the chemical formulae indicate that the solutions contain hydroxide ions, OH- (aq).

It is the presence of aqueous hydroxide ions, OH - (aq), that makes a solution an alkali.

The term ‘alkali’ is also used for compounds that dissolve in water to produce OH- (aq) ions, e.g. sodium hydroxide solid. The solid does not behave as an alkali unless water is present.

Name the ion that gives a solution the properties of an alkali.

Acids and Alkalis in Food

In S3, you tested some common food and drink items to determine their pH. We discovered that acid pH is good for preserving food, which is why some foods are pickled in vinegar, and citric acid can be added as a natural preservative. At the same time, some alkalis, like sodium hydrogen carbonate (bicarbonate of soda) can be added to create bubbles of carbon dioxide and make a foodstuff 'rise' or become less dense.

Bases

Acids have a pH less than 7; alkalis have a pH greater than 7; water and neutral solutions have a pH equal to 7.Alkalis can be thought of as ‘opposites’ to acids because they react with acids, moving the pH towards 7 and forming water. Any substance that reacts with acids in this way is called a base. As well as alkalis, metal oxides and metal carbonates are examples of bases.

Alkalis are a subset of the set of bases. Alkalis are the solutions formed when bases dissolve in water. Alkalis have a pH greater than 7 due to the concentration of OH- (aq) ions.

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Why can sodium hydroxide solution be described as ‘BOTH a base and an alkali’and yet nickel oxide can be described as ‘a base but NOT an alkali’?

Water

The chemical name for water is hydrogen oxide, H2O. With two non-metal elements, water can be expected to be made up of molecules with the atoms joined together by covalent bonds. Covalent compounds are non-conductors of electricity.

A sensitive meter can be used to show that water does conduct electricity although very poorly. This indicates that water does not just consist of molecules … a small number of ions must also be present in water.This is because a small number of molecules split up as follows:

H2O (l) H+ (aq) + OH- (aq) many water molecules very few ions

Since each water molecule can form one hydrogen ion, H+ (aq), and one hydroxide ion, OH- (aq), the concentration of hydrogen ions in pure water is equal to the concentration of hydroxide ions. Also, in a neutral solution, the concentration of hydrogen ions, H+ (aq) is equal to the concentration of hydroxide ions, OH- (aq).

In acids, the concentration of hydrogen ions, H+ (aq). is greater than the concentration of hydroxide ions, OH- (aq). When an acid solution is diluted, the concentration of H+ (aq) decreases.

In alkalis, the concentration of hydroxide ions, OH- (aq) is greater than the concentration of hydrogen ions, H+ (aq). When an alkaline solution is diluted, the concentration of OH- (aq) decreases.

It is important to remember that all solutions in water contain both hydrogen and hydroxide ions. It is the relative concentrations of these ions that decide whether a solution is acid, alkaline or neutral.

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BASES (react with acids forming water)

ALKALIS (a solution of a base)


Summary Exercise – Acids and Alkalis1. The pH scale is a continuous range from below to

above and measures the of a solution.2. Acids have a pH than 7, alkalis have a pH

than 7. 3. Pure water and solutions have a pH equal

to .4. Elements burn in oxygen to form

5. Non-metal oxides dissolve to form solutions and

metal oxides which dissolve in water form .6. All metal oxides and metal hydroxides are

because they react with acids to form salts.7. Acidic solutions contain lots of ions8. Alkaline solutions contain lots of ions.9. Dilution of an acid moves the pH towards and reduces

the concentration of ions.10.Dilution of an alkali moves the pH towards and

reduces the concentration of ions.11. If there are more hydrogen ions than hydroxide ions

present the solution is an . If there are more hydroxide ions than hydrogen ions the solution is an .

12. solutions and have equal numbers of hydrogen and hydroxide ions.

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13.Water exists mainly as with a fewwhich makes pure water a poor conductor.

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Neutralisation Revision

A base is a substance that reacts with an acid, decreasing the acidity. This kind of reaction is known as neutralisation (since the pH of the acid moves towards 7, the pH of a neutral solution). Water is one of the products of a neutralisation reaction and the other is a salt.

ACID + BASE SALT + WATER

Neutralisation of an acid involves the reaction of H+ (aq) ions with the base.

H+ (aq) + base salt + H2O

An alkali can also be neutralised by an acid.

OH- (aq) + acid salt + H2O

Many neutralisation reactions occur in everyday life. For example, bicarbonate of soda is a base used to neutralise acidic bee stings. Wasp stings, however, are basic and so acidic vinegar is used to neutralise a wasp sting. Toothpaste neutralises mouth acid to reduce tooth decay, and indigestion tablets neutralise excess stomach acid. Gardeners and farmers in Scotland can add basic 'gardener's lime' to the soil to reduce its acidity and make it suitable for growing different plants and crops.

Naming salts

An acid reacts with a base in a neutralisation reaction. A salt (as well as water) is formed. In the salt formation, the aqueous hydrogen ions in the acid, H+ (aq), are replaced by the positive metal ions (or ammonium ions) from the base. This gives the first part of the name of the salt.The second part of the name comes from the name of the negative ion in the acid.

Acid Negative ion

hydrochloric chloride

sulphuric sulphate

nitric nitrate

carbonic carbonate

phosphoric phosphate

Complete the table below.Name of acid Name of base Name of salt

sulphuric acid sodium oxide

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hydrochloric acid calcium hydroxide

nitric acid copper(II) oxide

phosphoric acid potassium carbonate

carbonic magnesium oxide

Reactions of AcidsMetal hydroxide solutions (alkalis), metal oxides and metal carbonates are all bases … they react with acids in a neutralisation reaction.

ACID + BASE SALT + WATER

If the base is a metal carbonate then carbon dioxide is also produced.

Many salts are prepared by neutralisation reactions. The method used to make the salt depends on its solubility, i.e. whether the salt is soluble or insoluble in water.

(a) The reaction of acid with alkali

ACID + ALKALI SALT + WATER

An indicator has to be used to find the volume of alkali required to neutralise a known volume of acid. The experiment is repeated using the same volume of alkali without the indicator. To obtain a solid sample of the salt, the salt solution is evaporated to dryness.

(b) The reaction of an acid with a metal oxide

ACID + METAL OXIDE SALT + WATER

This method can be used when the metal oxide is insoluble in water, e.g. copper(II) sulphate can be prepared by the reaction of copper(II) oxide with sulphuric acid. The metal oxide will react with the acid but will not dissolve in the neutral solution. If excess metal oxide is added (more than what is needed to react with all the acid), then the unreacted metal oxide can be removed from the neutral solution by filtering. The solution (the filtrate) is evaporated to dryness to obtain a solid sample of the salt.

(c) The reaction of an acid with a metal carbonate

ACID + METAL CARBONATE SALT + WATER + CARBON DIOXIDE

This method can also be used when the metal carbonate is insoluble in water, e.g. magnesium sulphate can be prepared by the reaction of magnesium carbonate with sulphuric acid. The method used is the same as that used with an insoluble metal oxide.

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d) Acids react with (some) metals to form a salt. The other product is hydrogen gas.

ACID + METAL SALT + HYDROGEN

In this reaction, the hydrogen ions, H+ (aq), react by gaining electrons and hydrogen molecules are formed.

2H+ (aq) + 2e- H2 (g)

The electrons come from the metal atoms as the atoms lose electrons to form metal ions.

This type of reaction is similar to neutralisation reactions since the H+ (aq) ions are ‘cancelled out’ and, as a result, the pH of the solution increases towards 7 as the reaction proceeds. However, the H+ (aq) ions form hydrogen gas, not water.

The method used to prepare a salt is the same as that used with an insoluble metal oxide and insoluble metal carbonate with the excess metal being filtered off.

Note that the reactions of dilute nitric acid with metals do not produce hydrogen gas.

Volumetric titrations

Acids and alkalis react to form a salt plus water in a neutralisation reaction.

Neutralisation is complete when all of the H+ (aq) ions from the acid have been “cancelled out” with exactly the same number of OH- (aq) ions from the alkali.

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

An indicator can be used to detect the end-point of the reaction.The number of moles of H+ (aq) that react will equal the number of moles of OH -

(aq) that react.The equipment used for a titration is shown below (see your notebook for the experiment):

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Conical flask with known volume of acid (unknown concentration) with few drops of indicator

Burette containing Alkali (known concentration)


We can use the results from you titration experiment to calculate the unknown concentration of acid. Your teacher will help complete this calculation

CalculationUsing balanced equationNaOH + HCl NaCl + H2O1 mole + 1 moleSo 1 mole of acid reacts with 1 mole of alkali.

First calculate the number of moles of alkali, using the equationn = c x v (Number of moles=concentration x volume) V = 10.0ml or 10/1000L for sodium hydroxideC = concentration of sodium hydroxide = mol/l

n = ________________moles of alkali

We can use the result for number of moles, as this is the same for both acid and alkali (as from balanced equation 1 mole of alkali reacts with 1 mole of acid). To calculate the concentration of acid in your titration:

n = number of moles (already calculated above) = molesV = average titre reading from experiment = LC = concentration of acid used in experiment

C = n/ v =

Spectator ions: neutralisation reactionsSpectator ions are ions that do not take part in a chemical reaction. The idea of spectator ions can be understood by looking at neutralisation reactions.

(a) Reaction of a dilute acid with an alkalie.g. the reaction of sodium hydroxide solution with dilute hydrochloric acid

HCl (aq) + NaOH (aq) NaCl (aq) + H2O (l)

This equation can be rewritten to show the ions present.

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Since water is made up almost entirely of molecules (covalent bonding) it is left unchanged.

H+ (aq) and Cl- (aq) + Na+ (aq) and OH- (aq)

Na+ (aq) and Cl- (aq) + H2O (l)

Both the Na+ (aq) and Cl- (aq) have not changed during the reaction. These ions are both spectator ions and can be cancelled out to show the actual reaction taking place.

H+ (aq) and Cl- (aq) + Na+ (aq) and OH- (aq)

Na+ (aq) + Cl- (aq) + H2O (l)

hence H+ (aq) + OH- (aq) H2O (l)

This equation shows the OH- (aq) of the alkali reacting with the H+ (aq) of the acid. It is called an ion equation. The ion equation shows the ions that take actually take part in the reaction. The ion equation is the same for the neutralisation of any acid with any alkali.

(b) Reaction of a dilute acid with a metal carbonatee.g. the reaction of dilute sulphuric acid with sodium carbonate solution

H2SO4 (aq) + Na2CO3 (aq) Na2SO4 (aq) + H2O (l) + CO2 (g)

Both water and carbon dioxide are made up of molecules (covalent bonding).

Rewriting to show the ions present gives:

2H+ (aq) and SO42- (aq) + 2Na+ (aq) and CO32- (aq)

2Na+ (aq) and SO42- (aq) + H2O (l) + CO2 (g)

Both the Na+ (aq) and the SO42- (aq) are spectator ions and can be cancelled out.

2H+ (aq) and SO42- (aq) + 2Na+ (aq) and CO32- (aq)

2Na+ (aq) and SO42- (aq) + H2O (l) + CO2 (g)

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The ion equation shows what actually happens in the reaction of a dilute acid with a solution of a metal carbonate.

2H+ (aq) + CO32- (aq) H2O (l) + CO2 (g)

Insoluble Products - Precipitation ReactionsSome ionic solids are soluble in water. The combination of positive and negative ions separate as the solid dissolves, e.g. A+ X- (s) and B+ Y- (s). When solutions of these ions are mixed, the combination of A+ (aq) and Y- (aq) is insoluble in water and the ions come together to form a solid, A+ Y- (s).

The insoluble solid that settles out of the solution is called a precipitate. This can be separated from the solution by filtration. The kind of reaction that takes place is known as precipitation.

The precipitate takes its name from the metal ion in one solution and the negative ion in the other. e.g. silver nitrate solution + sodium chloride solution

silver chloride solid + sodium nitrate solution

The Data Booklet, p 8 , can be used to find out which product, if any, will occur as a precipitate. Take ‘i’ to be insoluble, i.e. the solid will form as a precipitate.

Insoluble salts can be prepared by precipitation.

Spectator ions: precipitation reactionsThe idea of spectator ions can also be applied to precipitation reactions,e.g. the reaction of sodium chloride solution with silver nitrate solution produces a precipitate of silver chloride.

The balanced equation with state symbols is:

NaCl (aq) + AgNO3 (aq) NaNO3 (aq) + AgCl (s)

In solution, the ions in an ionic compound are free to move whereas the ions in a solid are tightly packed together.

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A+ (aq) X- (aq) B+ (aq) Y- (aq)B+ (aq) X- (aq)

A+ Y- (s)


Na+ (aq) and Cl- (aq) + Ag+ (aq) and NO3- (aq)

Na+ (aq) and NO3- (aq) + Ag+ Cl- (s)

The spectator ions are the Na+ (aq) and NO3- (aq) and these ions can be cancelled out.

Na+ (aq) and Cl- (aq) + Ag+ (aq) and NO3- (aq)

Na+ (aq) and NO3- (aq) + Ag+ Cl- (s)

hence Cl- (aq) + Ag+ (aq) Ag+Cl- (s)

This equation shows the ions that actually react.

In any precipitation reaction,

A+ X- (aq) + B+ Y- (aq) A+ Y- (s) + B+

X- (aq)

the spectator ions can be cancelled out to leave:

A+ (aq) + Y- (aq) AY (s)

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Summary File - Neutralisation1.A neutralisation reaction occurs when a reacts with

and acid and the pH moves towards .2.Bases that dissolve in water are typically group metals

and .3.Chloride salts are formed from acid, salts are formed from sulphuric acid and nitrate

salts are made from acid.4.Everyday examples of neutralization include the addition of to treat acidic soil and the use of to treat

alkaline wasp stings.5. One of the main industrial uses for salt is the preparation of . This is an everyday example of .6.Acid rain is produced when is

dissolved in rain water. One of the problems that acid rain can cause is damage to buildings containing rocks.

7.The products of a metal carbonate and acid neutralisation reaction are , and . The test for the gas produced is

8.The products of a metal oxide and acid neutralisation reaction are and .

9.The products of a metal and acid neutralisation reaction are and . The test for the gas produced is 10. The more reactive metals which react with acids including

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, , , and .

11. In a neutralisation reaction the ions from the acid react with the ions from an alkali to form water molecules.

12. A spectator ion is something which remains at start and end of a reaction .

13. Soluble salts can be prepared by titration are by reacting an acid with insoluble or .

14. Precipitation is the method used to prepare salts. Two solutions are mixed together to form an salt which can be removed from the mixture by .

15. The relationship between number of moles, volume and concentration can be represented by the equation .

16. A chemical change can be described as is heat is given out to the surroundings. Reactions which take in heat are described as reactions.

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Acids and Bases - Glossary

Word Meaning

AcidA substance with pH less than 7, because it contains more H+ than pure water.

AlkaliA substance with pH greater than 7, because it contains less H+ than pure water.

Household AcidSubstance used in the home with a pH less than 7. e.g. lemon juice.

Laboratory AcidSubstance used in the lab with a pH less than 7. e.g. sulphuric acid.

Household AlkaliSubstance used in the home with a pH greater than 7. e.g. Bleach

Laboratory AlkaliSubstance used in the lab with a pH greater than 7. e.g. sodium hydroxide.

pH scaleA measure of the acidity of a substance, ranging from 0 to 14.

pH chartA colour chart showing the colour produced by an indicator at different pH values.

Acidic gases

Oxides of non metals which produce acid solution when they dissolve in water in the atmosphere.

Acid RainRain, fog, snow or hail which has a pH less than 7.

Soluble Metal Oxide Oxide which dissolves to make an alkali.Soluble Non-Metal Oxide Oxide which dissolves to make an acid.

NeutralisationThe reaction of an acid to produce a salt and water.

PrecipitationA reaction in which 2 solutions produce an insoluble solid.

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Word Meaning

Spectator ionIon which appears unchanged on both sides of the reaction equation.

ConcentrationThe number of moles of solute dissolved in a litre of solution (mol/l)

Indicator A substance whose colour depends on pHStandard Solution Solution of known concentration.

Titration

An experiment using a burette and pipette to accurately measure the volumes needed to complete a reaction.

Base Any substance which neutralises an acid.

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elements, mixtures and · web viewit is not just copper(ii) oxide and zinc oxide that have ......

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