Chapter 18

Question 1

Test for hydrogen

Answer 1

Put out lighted splint with squeaky pop

Question 2

Equation for hydrogen test

Answer 2

2H2*O2-> 2H20

Question 3

Test for oxygen

Answer 3

Glowing splint relights

Question 4

Test for Carbon Dioxide

Answer 4

Bubbled through limewater

Question 5

Equation for Carbon Dioxide

Answer 5

Ca(OH)2(aq)+CO2(g)+CO2(g) —> CaCO3(s)+H2O(l)

Question 6

Test for Chlorine

Answer 6

Blue litmus paper turns red then bleaches white

Question 7

Test for ammonia

Answer 7

Red litmus paper turns blue

Question 8

Test for water

Answer 8

White anhydrous copper sulphate would turn blue

Question 9

Equation for water test

Answer 9

CuSO4+5H2O—>CuSO4.5H2O

left: anhydrous, right: hydrated

Question 10

Flame tests can be used to identify what?

Answer 10

metal ions eg lithium, sodium, potassium, calcium and compounds

Question 11

How do flame tests work?

Answer 11

• Dip the flame test wire into concentrated hydrochloride acid then hold it in the non-luminous (blue) Bunsen flame to clean it
• Dip the wire back into the acid then into the solid being tested
• Hold the wire in the non-luminous flame

Question 12

Lithium ion colour

Answer 12

Red/ crimson

Question 13

Sodium ion colour

Answer 13

Yellow

Question 14

Potassium ion colour

Answer 14

Lilac

Question 15

Calcium ion colour

Answer 15

Orange - red

Question 16

Copper ion colour

Answer 16

Blue green

Question 17

Testing for positive ions using sodium hydroxide how:

Answer 17

• add a few drops of sodium hydroxide solution to the solution being tested

Question 18

Why does the sodium hydroxide test work?

Answer 18

Most metal hydroxides are insoluble and transition metal ions form coloured precipitates with sodium hydroxide

Question 19

Copper Sulphate + Sodium hydroxide —>

Answer 19

Copper hydroxide + sodium sulphate