Group 7

Question 1

Give the products of this equation:

NaCl (s) + H2SO4 (aq) —>

Answer 1

NaHSO4 (s) + HCl (g)

Question 2

State the observation for this reaction:

NaCl (s) + H2SO4 (aq) —> NaHSO4 (s) + HCl (g)

Answer 2

Steamy Fumes

Question 3

Give the half equation for the oxidation of bromide ions?

Answer 3

2Br- —> Br2 + 2e-

Question 4

What are the observed when bromide ions react with sulphuric acid in a redox reaction?

Answer 4

Acidic Gas (SO2)
Brown Fumes (Br2)

Question 5

State the 3 different sulphur products that can be formed with iodide ions reacts with H2SO4?

Answer 5

Sulphur Dioxide (SO2)
Sulphur (S)
Hydrogen Sulphide (H2S)

Question 6

What is the observation when iodine is formed in a reaction with H2SO4?

Answer 6

Black solid

Question 7

The student noticed some of the liquid injected into a gas syringe didn’t vaporise. Explain the effect this has on the Mr calculated by the student?

Answer 7

Lower volume recorded so Mr increases

Question 8

What’s the observation of:

• H2S
• S
• SO2

Answer 8

• Bad-Egg Smell
• Yellow Solid
• Acidic Gas

Question 9

What is the test for halide ions?

Why is this needed?

Answer 9

Acidified Silver Nitrate (AgNO3)

To remove carbonate ions

Question 10

What is observed when dilute ammonia (NH3) is added to AgCl?

Answer 10

White precipitate dissolves

Question 11

What is observed when dilute ammonia (NH3) is added to AgBr?

Answer 11

Cream precipitate remains

Question 12

What is observed when concentrated ammonia (NH3) is added to AgBr?

Answer 12

Cream precipitate dissolves

Question 13

What is observed when concentrated ammonia (NH3) is added to AgI?

Answer 13

Yellow precipitate remains

Question 14

Why is chlorine added to drinking water?

Answer 14

To kill bacteria

Question 15

Cl2 (g) + H2O (l)

Answer 15

<—> HClO (aq) + HCl (aq)

Question 16

Cl2 (g) + H2O (g) —>

Answer 16

HCl + O2 ——> balance

Question 17

Cl2 (g) + 2NaOH (aq) —>

Answer 17

NaClO + NaCl + H2O

Question 18

Chlorine is toxic. Why is it not dangerous to add it to drinking water?

Answer 18

Not toxic once added in low concentrations

Question 19

State the observation for:

Cl2 + 2NaBr —> Br2 + 2NaCl

Answer 19

Orange/Brown solution

Question 20

State the observation for:

Cl2 + 2NaI —> I2 + 2NaCl

Answer 20

Brown solution

Question 21

State the observation for:

I2 + 2NaCl —>

Answer 21

No reaction (brown solution remains)

Question 22

Cl2 + NaBr —>

Answer 22

Br2 + 2NaCl

Question 23

What is the observation when sodium carbonate is added to an acid?

Answer 23

Effervescence (CO2 gas is released)

Question 24

What is the reagent used to test for ammonium ions?

Answer 24

Heat with NaOH

Question 25

What is observed when ammonium (NH4+) ions are heated with NaOH?

Answer 25

Gas released turns damp red litmus paper blue

Question 26

What gas is released when ammonium ions are warmed with NaOH?

Answer 26

Ammonia Gas (NH3)

Question 27

Outline a logical sequence of test-tube reactions for sodium carbonate, sodium fluoride and sodium chloride that the student could carry out to identify each of these compounds.
Include the observations the student would expect to make.
Give equations, including state symbols, for any reactions that would take place. (6)

Answer 27

Stage 1 - suggested tests:
1a Add nitric acid to all 3
1b Add water / make into a solution
1c Add AgNO3

Stage 2 - expected observations:
2a Sodium Carbonate will fizz with acid
2b NaCl gives white ppt with AgNO3
2c NaF shows no (visible) change

Stage 3 Equations – state symbols must match method
3a Na2CO3 + 2HNO3 → 2NaNO3 + CO2 + H2O
3b AgNO3 + NaCl → AgCl + NaNO3
3c correct state symbols