Chemical Changes

Question 1

You can measure the pH of a solution, using what?

Answer 1

Universal indicator

Question 2

Acid + base =

Answer 2

Salt + water

Question 3

What can acids produce in water?

Answer 3

Produce protons

Question 4

Acids can be strong or weak

Answer 4

Strong acid (hydrochloric acid)
Weak acid (citric acid)

Question 5

What is pH a measure of?

Answer 5

Measure of the concentration of Hydrogen ions

Question 6

Factor H+ ion concentration changes by 10^-x

Answer 6

X is the difference in pH. So if pH falls from 7 to 4 the difference is -3, and the factor the H+ ion concentration has increased by is 10^-(-3) = 10^3 = 1000

Question 7

Do not confuse strong acids with concentrated acids

Answer 7

Acid strength tells you what proportion of the acid molecules ionise in water.
The concentration of an acid is different. It measure how much acid there is in a certain volume of water. Concentration is basically how watered down your acid is.

Question 8

Acid + Metal =

Answer 8

Salt + water

Question 9

Acid + metal hydroxide =

Answer 9

Salt + water

Question 10

Acid + metal carbonate =

Answer 10

Salt + water + carbon dioxide

Question 11

You can make soluble salts using an insoluble base. Practical.

Answer 11

1) pick right acid and insoluble base, eg to make copper chloride, tou could mix hydrochloric acid and copper oxide
2) Gently warm dilute acid, then turn bunsen burner off.
3) add the insoluble base to the acid a bit at time, until no more reacts. You’ll know when all the acid has been neutralised because, even after stirring, the excess solid will just sink to the bottom.
4) then filter out excess solid to get salt solution
5) to get pure, solid crystals of salt, gently heat the solution using a water bath. Then crystallisation.

Question 12

Acid + metal =

Answer 12

Salt + Hyrdrogen

Question 13

Metal + water =

Answer 13

Metal Hydroxide + Hydrogen

Question 14

Oxidation

Answer 14

Gain of oxygen

2Mg + O2 = 2MgO

Question 15

Reduction

Answer 15

Loss of oxygen

2CuO + C = 2Cu + CO2

Question 16

Some metals can be extracted by reduction with carbon. Explain.

Answer 16

Metals below carbon in the reactivity series can be extracted by reduction using carbon.
Metals higher than than carbon in the reactivity can be extracted by reduction using carbon

Question 17

If electrons are transferred, what is it called?

Answer 17

A redox reaction

This is where reduction and oxidation of electrons happen at the same time

Question 18

Displacement reactions are?

Answer 18

Redox reactions

A more reactive metal will displace a less reactive metal from its compound

Question 19

Electrolysis

Answer 19

Splitting up with electricity

Question 20

What is produced at cathode?

Answer 20

Positive ions and gain electrons (they are reduced)

Question 21

What is produced at the cathode?

Answer 21

Negative ions and lose electrons (they are oxidised)

Question 22

Electrolysis of molten ionic solids forms elements

Answer 22

An ionic solid can’t be electrolysed because the ions are in a fixed position and cant move. Molten ionic compounds can be electrolysed because the ions can move freely and conduct electricity.

Question 23

Metals can be extracted from their ores using electrolysis

Answer 23

If a metal is too reactive to be reduced with carbon or reacts with carbon, then electrolysis can be used to extract it