C2.6 Acids, bases and salts

Question 1

What does the pH scale measure?

Answer 1

how acidic or alkaline a solution is

Question 2

What are the 3 ways soluble salts can be made?

Answer 2

reacting acid with:

• metals
• insoluble bases
• alkalis

Question 3

Describe how a soluble salt can be made by reacting acid with metal

Answer 3

Add metal to acid (metal needs to be more reactive than hydrogen)

metal will dissolve in acid as it reacts

filter out excess metal that has not dissolved to get salt solution

crystallisation- evaporate som of the water with a bunsen burner then leave to evaporate naturally to get cure, solid crystals of the salt.

Question 4

What is the word equation for reacting a metal with acid?

Answer 4

acid + metal —– salt + hydrogen

Question 5

What are the 4 state symbols and what do they stand for?

Answer 5

(s) solid
(l) liquid
(g) gas
(aq) aqueous - dissolved in water

Question 6

In a reaction, the more reactive the metal…

Answer 6

the faster the rate of reaction

Question 7

Why does copper not react with acids?

Answer 7

as it is less reactive than hydrogen

Question 8

What is the test for hydrogen?

Answer 8

the burning split test- gives a squeaky pop

Question 9

What type of salt will hydrochloric acid produce?

Answer 9

a chloride

Question 10

What type of salt will sulfuric acid produce?

Answer 10

a sulfate

Question 11

what type of salt does nitric acid produce?

Answer 11

a nitrate

Question 12

What is an insoluble base?

Answer 12

a metal oxide or metal hydroxides

Question 13

Describe the reaction with an insoluble base (metal oxide or metal hydroxide) and acid

Answer 13

Add insoluble base to acid. It will dissolve in the acid as it reacts.

You will know when all the acid has been neutralised because the excess solid will just sink to the bottom of the flask

excess solid filtered off to get salt solution

crystallisation- evaporate some of the water then leave the rest to evaporate slowly to get pure, solid crystals of salt

Question 14

What is the word equation for reacting an insoluble base with a metal?

Answer 14

acid + insoluble base ——- salt + water

Question 15

Describe how alkalis can be used to make salts?

Answer 15

Add alkali to an acid. Use an indicator to show when neutralisation has occurred

repeat using exact same volume of acid and alkali so the salt is not contaminated with indicator

crystallisation

Question 16

What is the word equation of reacting an acid with an alkali?

Answer 16

Acid + Alkali = Salt + Base

Question 17

Describe crystallisation

Answer 17

used to produce solid salts

evaporate some of water with a bunsen burner to make the solution more concentrated

leave the rest to evaporate slowly

Question 18

what is a soluble salt?

Answer 18

a salt dissolved in water

Question 19

What is an insoluble salt?

Answer 19

A salt which does not dissolve in water

Question 20

What kind of reaction do you do if the salt you want to make is insoluble?

Answer 20

precipitation reaction

Question 21

Describe how insoluble salts can be made

Answer 21

a precipitation reaction

by mixing appropriate solutions of ions so that a precipitate is formed.

filter salt from solution

Question 22

Describe how you would make lead chloride

Answer 22

need a solution that contains lead ions and chloride ions.

Therefore, could mix lead nitrate solution with sodium chloride solution

Question 23

Give an example of when precipitation reactions are used

Answer 23

used to remove unwanted ions from solutions

eg in treating water for drinking or in treating effluent

Question 24

what are bases?

Answer 24

metal oxide and hydroxides

Question 25

what is an alkali?

Answer 25

soluble hydroxide

Question 26

What charge are hydrogen (H) ions?

Answer 26

positive

Question 27

What charge are hydroxide ions (OH)?

Answer 27

negative

Question 28

What do acids form in water?

Answer 28

H + ions

Question 29

What do alkalis form in water?

Answer 29

OH - ions

Question 30

H+ make solutions……

Answer 30

Acidic

Question 31

OH- ions make solutions ….

Answer 31

alkali

Question 32

What does the salt produced in a reaction between an acid and base or alkali depend on?

Answer 32

• the acid used (eg hydrochloric acid produces chlorides)

- The metal in the base or alkali

Question 33

Describe the use of ammonia

Answer 33

ammonia dissolves in water to produce an alkali solution ( ammonium hydroxide).

It is used to produce ammonium salts (ammonium nitrate) by reacting ammonium hydroxide with nitric acid

Ammonium salts are important as FERTILISERS

Question 34

Describe the pH scale

Answer 34

1-6 is acid

7- neutral

8-14- alkali

Question 35

Describe a neutralisation reaction and give the equation

Answer 35

hydrogen ions react with hydroxide ions to produce WATER

H+ (aq) + OH- (aq) ——- H20

Question 36

Explain why a solution may turn cloudy?

Answer 36

Because a precipitate has been formed

Question 37

What is the ionic equation for the neutralisation reaction?

Answer 37

H+ + OH- ———– H2O

Question 38

What is the chemical formula for sulfuric acid?

Answer 38

H2SO4

Question 39

ammonia + …………….. acid ———- ammonium nitrate

Answer 39

nitric

Question 40

Why do some farmers put ammonium nitrate on their farmland?

Answer 40

because it is a fertiliser so helps plants to grow

Question 41

Explain why it would not be suitable for a student to react potassium with an acid

Answer 41

potassium is very reactive

so would be dangerous