2.6 Acids, bases and salts

BTEOTSSSBAT:Know that acidic and alkaline solutions are

measured on the pH scale

Identify an acid or alkali given the pH number

Know the ions that make a solution acidic or alkali

Know the products of an acid and a base reaction

Key words

Acid

Alkali

Neutral

pH scale

Base

Salt

The pH scale

pH is a measure of how acidic or alkali a solution is.

PH 7 = neutral

Indicator solution changes colour according to the

pH

Acids Alkalis

Neutral

The pH scale

pH < 7 pH > 7

pH = 7

Vinegar

Can you place the above in order in the pH scale?

The pH scale

Stomach

acid

Distilled

water Soap

powder

BleachLemon juice

Vinegar

The pH scale

Stomach

acidDistilled

water

Soap

powderBleach

Lemon juice

Acids and Alkalis

What is it that determines if a solution is acid or alkali?

It’s the type of ion

H+(aq) ions make solutions acidic

and

OH–(aq) ions make them alkaline.

NB (aq) is a state symbol and it means that the

substances are in solution (aqueous)

Neutralisation

When does red + blue = green?

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

When it’s a neutralisation

An acid and a base react to form a salt and water

Acid + Base Salt + Water

Acid or alkali?

Lemon juicepH = 4

pH = 8H+ (aq)

OH- (aq)Bleach Indicator turns blue

Indicator turns yellow

Acid Alkali

Sour taste Soapy feel

Acid or alkali?

Acid Alkali

pH = 4 pH = 8

H+ (aq) OH- (aq)

BleachLemon juice

Indicator turns blueIndicator turns yellow

Sour taste Soapy feel

Quick test

pH scale

1. What is the name of the scale that

measures acidity or alkalinity?

Quick test

pH = 7

2. If a solution is neutral what is its pH?

Quick test

3. Which ion makes a solution acidic?

H+ (aq)

Quick test

4. Which ion makes a solution alkali?

OH- (aq)

Quick test

Acid + Base Salt + Water

5.What is formed when an acid and a

base react?

Quick test

Bases that are solutions are alkalis

All alkalis are bases but not all bases

are alkalis

6. What is the difference between

an alkali and a base?

2.6 Acids, bases and salts

BTEOTSSSBAT:Know how to make soluble salts

Know that metal oxide and metal hydroxides are

bases

Know how to make salts from metal oxides and

hydroxides

Know which salts are formed when metals and

acids react

Making soluble salts using neutralisation

Making soluble salts:

Reacting an acid with a metal or with an insoluble base

to give a soluble salt

Preparing an Insoluble Salt

S t r e t c h q u e s t i o n

Lead iodide is formed via precipitation by mixing aqueous

lead(II) nitrate (Pb(NO3)2) and aqueous potassium iodide

(KI)

What is meant by precipitation?

A precipitate is a solid that forms

What does the (II) in lead (II) nitrate mean?

The II show that the lead has a ionic charge of 2+

Balance the equation for this reaction.

Pb(NO3)2 + KI → PbI2 + KNO3

Add the state symbols (s) (l) (g) or (aq) for each

compound.

22

Pb(NO3)2 + 2KI → PbI2 + KNO3(aq)(aq) (aq)(s)

Find the Mr for each of the substances.

The Ar of Pb = 207

The Ar of K = 39

The Ar of I = 127

The Ar of N = 14

The Ar of O= 16

Pb(NO3)2 + 2KI → PbI2 + KNO3

207 + (14+3 x 16) x 2

331

39 + 127

166

207 + 2 x 127

461

39 + 14+ 16 x 3

101

What percentage of Iodine is there in lead iodine?

Pb(NO3)2 + 2KI → PbI2 + KNO3

How much would 1 mol of lead nitrate weigh?

331 166 461 101

Out of the 461 iodine is 2 x 127 so

127 x 2 x 100 = 55.1%

461

Mr = 331 so 331 g

25 g of lead nitrate is reacted to produce the lead

iodine. How much lead iodine will be produced?

Pb(NO3)2 + 2KI → PbI2 + KNO3

331 166 461 101

331g would produce 461g

1g would produce 461/ 331

25g would produce (461/ 331) x 25 g

= 34.8g

If 30g of lead iodine is produced calculate

the percentage yield.

Why might the yield be less than 100%?

34.8g is the predicted grade30g is the actual grade

30 x 100%

34.8

= 86.2%

K has an atomic number of 19. Draw its electron

structure and state which period and group it is in.

Give reasons for your answer.

4 shells so period 41 electron in outer shell so group 1

S t r e t c h q u e s t i o n

Barium chloride and sodium sulphate are mixed. A precipitate of barium sulphate and sodium chloride is formed.

Balance the equation for this reaction

BaCl2(aq) + Na2SO4 (aq) ------> BaSO4(s) + NaCl(aq)2

The (aq) symbol means aqueous. What does this mean?

The barium chloride is in solution

Find the Mr for each of the substances.

The Ar of Pb = 207

The Ar of K = 39

The Ar of I = 127

The Ar of N = 14

The Ar of O= 16

Pb(NO3)2 + 2KI → PbI2 + KNO3

207 + (14+3 x 16) x 2

331

39 + 127

166

207 + 2 x 127

461

39 + 14+ 16 x 3

101

What percentage of Iodine is there in lead iodine?

Pb(NO3)2 + 2KI → PbI2 + KNO3

How much would 1 mol of lead nitrate weigh?

331 166 461 101

Out of the 461 iodine is 2 x 127 so

127 x 2 x 100 = 55.1%

461

Mr = 331 so 331 g

25 g of lead nitrate is reacted to produce the lead

iodine. How much lead iodine will be produced?

Pb(NO3)2 + 2KI → PbI2 + KNO3

331 166 461 101

331g would produce 461g

1g would produce 461/ 331

25g would produce (461/ 331) x 25 g

= 34.8g

If 30g of lead iodine is produced calculate

the percentage yield.

Why might the yield be less than 100%?

34.8g is the predicted grade30g is the actual grade

30 x 100%

34.8

= 86.2%

A bee sting is acidic

A wasp sting is alkaline

What everyday substances could be used to

treat each of the stings?

Barium chloride and sodium sulphate are mixed.

A precipitate of barium sulphate and sodium chloride is formed.

Balance the equation for this reaction

BaCl2(aq) + Na2SO4 (aq) ------> BaSO4(s) + NaCl(aq)

The (aq) symbol means aqueous. What does this

mean?

Name the two reactants in the reaction

Name the two products in the reaction

Barium sulphate is a precipitate – what does the

term precipitate mean?

In solution

Barium chloride and sodium sulphate

A solid forms

barium sulphate and sodium chloride

Use the following information to answer the next question

Ar of Ba = 137 Ar of S = 32

Ar of Cl = 35.5 Ar of O = 16

Find the formula mass of each of these compounds involved in the reaction.

BaCl2 BaSO4

What is percentage of barium is in (a) barium chloride and (b) barium sulfate

How much would 1 mol of barium chloride weigh?

What is the mass of one mole of barium chloride?

30 g of barium sulphate is reacted in an excess of sodium sulphate to

produce barium sulphate. How much barium sulphate will be produced?

If 32 g of barium sulphate is produced calculate the percentage yield.

208 233

65.9% 58.8%

208g

233g

233/ 208 x 30 = 33.6g

32/33.6 x 100 = 95.2%