Introducing Acids and Introducing Acids and BasesBases

Chapter 13Chapter 13

AcidsAcids

Acids are commonly used in our homes.Acids are commonly used in our homes. They are used in many foods to enhance the flavour, the They are used in many foods to enhance the flavour, the

sour tastes in many foods is due to their acid content.sour tastes in many foods is due to their acid content. Vinegars have ethanoic acid, orange juice contains citric Vinegars have ethanoic acid, orange juice contains citric

acid and soft drinks contain carbonic acid.acid and soft drinks contain carbonic acid.

AcidsAcids Acids in foods are not strong. Acids in foods are not strong. Can anyone tell me three common Can anyone tell me three common

laboratory acids.laboratory acids. Acids can be dangerous when Acids can be dangerous when

misused. They can cause severe misused. They can cause severe burns due to corrosion.burns due to corrosion.

Acid rain causes soils to become Acid rain causes soils to become ‘sour’ and stunts plant growth.‘sour’ and stunts plant growth.

Properties of AcidsProperties of Acids In general, acids can:In general, acids can:

Change the colour of some indicatorsChange the colour of some indicators Be corrosiveBe corrosive Taste sourTaste sour React with basesReact with bases Have a relatively low pHHave a relatively low pH

BasesBases React with acids. React with acids. Can be just as dangerous as acids. Can be just as dangerous as acids. Bases are effective cleaners because Bases are effective cleaners because

they can react with fats or oils to they can react with fats or oils to produce water soluble soaps.produce water soluble soaps.

BasesBases In general bases can:In general bases can:

Turn litmus paper blueTurn litmus paper blue Have a slippery feelHave a slippery feel Are caustic Are caustic React with acidsReact with acids Have a relatively high pHHave a relatively high pH

NeutralisationNeutralisation When an acid and base react to form a When an acid and base react to form a

solution of salt and water. solution of salt and water. This is called neutralisation.This is called neutralisation. Acids and bases are said to neutralise each Acids and bases are said to neutralise each

other. other. That is the eliminate each others properties.That is the eliminate each others properties. Some neutralisation reactions are very Some neutralisation reactions are very

dangerous however.dangerous however.

SafetySafety Wear safety glassesWear safety glasses Wear a lab coatWear a lab coat Label bottles and containers.Label bottles and containers. If possible store separatelyIf possible store separately When diluting acids, add the acid to the When diluting acids, add the acid to the

water and not the water to the acid.water and not the water to the acid. Why might we use these precautions?Why might we use these precautions?

IndicatorsIndicators A substance that has different colours A substance that has different colours

depending on its acid or base form.depending on its acid or base form. Litmus paper is red for acids and blue Litmus paper is red for acids and blue

for bases. for bases. Indicators themselves can be acids or Indicators themselves can be acids or

bases. bases. They change from one colour in acid They change from one colour in acid

to another one in basic solutions to another one in basic solutions

IndicatorsIndicators

Reactions involving acids and Reactions involving acids and basesbases

Before we begin you need Before we begin you need to note that when we say a to note that when we say a salt. It does not mean table salt. It does not mean table salt that you put on your salt that you put on your chips.chips.

It does not mean NaCl.It does not mean NaCl. A salt can be a compound A salt can be a compound

that is derived from an that is derived from an acid. acid.

Salts are usually made up Salts are usually made up of a metal cation and a non-of a metal cation and a non-metal anion.metal anion.

The salt produced will The salt produced will depend on the acid used.depend on the acid used.

Reaction Type 1Reaction Type 1 Acid + reactive metal Acid + reactive metal ―› salt + hydrogen―› salt + hydrogen

Reactive metals include Ca, Mg, K and Zn but Reactive metals include Ca, Mg, K and Zn but not Cu, Ag or Aunot Cu, Ag or Au

For exampleFor example2HCl(aq) + Zn(s) ―› ZnCl2HCl(aq) + Zn(s) ―› ZnCl22(aq) + H(aq) + H22 (g) (g)

Who can write this equation as an ionic Who can write this equation as an ionic equation??equation??

Reaction Type 2Reaction Type 2 Acid + metal hydroxide Acid + metal hydroxide ―› salt + water―› salt + water

Metal hydroxides include NaOH, Ca(OH)Metal hydroxides include NaOH, Ca(OH)22 and Mg(OH)and Mg(OH)22..

For exampleFor exampleHH22SOSO44(aq) + 2NaOH(aq) ―› Na(aq) + 2NaOH(aq) ―› Na22SOSO44(aq) + 2H(aq) + 2H22O(l)O(l)

Write the ionic equation and write the spectator Write the ionic equation and write the spectator ions down.ions down.

Reaction Type 3Reaction Type 3 Acid + metal oxide Acid + metal oxide ―› salt + water―› salt + water

Metal oxides include NaMetal oxides include Na22O, MgO, CaO O, MgO, CaO and ZnOand ZnO

Give me an example of an equation if Give me an example of an equation if nitric acid reacts with solid calcium nitric acid reacts with solid calcium oxide.oxide.

Reaction Type 4Reaction Type 4 Acid + metal carbonate Acid + metal carbonate ―› salt + water + carbon ―› salt + water + carbon

dioxidedioxide Metal carbonates include NaMetal carbonates include Na22COCO33, MgCO, MgCO33 and and

CaCOCaCO33

Show an equation for nitric acid reacting with Show an equation for nitric acid reacting with MgCOMgCO33..

Show both the balanced equation and the ionic Show both the balanced equation and the ionic equation.equation.

Reaction Type 5Reaction Type 5 Acid + metal hydrogen carbonate Acid + metal hydrogen carbonate ―›―›

salt + water + carbon dioxidesalt + water + carbon dioxide Metal hydrogen carbonates include Metal hydrogen carbonates include

NaHCONaHCO33, KHCO, KHCO33 and Ca(HCO and Ca(HCO33))22..

HCl(aq) + NaHCOHCl(aq) + NaHCO33(aq) ―› NaCl(aq) + H(aq) ―› NaCl(aq) + H22O(l) + COO(l) + CO22(g)(g)

Ionic EquationIonic EquationHH++(aq) + HCO(aq) + HCO33--(aq) ―› H(aq) ―› H22O(l) + COO(l) + CO22(g)(g)

Reaction Type 6Reaction Type 6 Acidic oxide (non-metal oxide) + Acidic oxide (non-metal oxide) +

base base ―› salt + water―› salt + water Acidic oxides include SOAcidic oxides include SO22, SO, SO33, P, P44OO1010 and and

COCO22..

COCO22(aq) + Ca(OH)(aq) + Ca(OH)22(aq) ―› CaCO(aq) ―› CaCO22(aq) + (aq) + HH22O(l)O(l)