G7 Reactions

Question 1

NaF + H2SO4

Answer 1

NaF (s) + H2SO4(aq) —> NaHSO4(s) + HF(g)
Acid base reaction
Observation - steamy white fume

F- acts as base

Question 2

NaCl + H2SO4

Answer 2

NaF (s) + H2SO4(aq) —> NaHSO4(s) + HF(g)
Acid base reaction
Observation - steamy white fume

Cl- acts as a base

Question 3

NaBr + H2SO4

Answer 3

NaBr(s) + H2SO4(aq) —> NaHSO4(s) + HBr(g)
Acid base reaction
Observation - steamy white fume

Question 4

Equation for SO2 reduction from H2SO4

Answer 4

H2SO4 + 2H+ + 2e- —> SO2 + 2H2O

Question 5

Equation for S reduction from H2SO4

Answer 5

H2SO4 + 6H+ + 6e- —> S + 4H2O

Question 6

Equation for H2S reduction from H2SO4

Answer 6

H2SO4 + 8H+ + 8e- —> H2S + 4H2O

Question 7

Halide ion test

Answer 7

1. Solution acidified with dilute nitric acid (removed unwanted silver compounds)
2. Silver nitrate added

Question 8

Halide ion test results

Answer 8

HCl = white precipitate
HBr = cream precipitate
HI = yellow precipitate

Question 9

Additional test for silver halides

Answer 9

Add dilute and concentrated ammonia to 2 separate samples of all the AgHalides

Question 10

Additional test for silver halides result (dilute)

Answer 10

Cl- = soluble
Br- = sparingly soluble
I- = insoluble

Question 11

Additional test for silver halides result (conc)

Answer 11

Cl- = soluble
Br- = soluble
I- = insoluble

Question 12

Test for chlorine (2)

Answer 12

Blue litmus paper turns red due to H+ ions send turns white a Cl2 bleach the paper.

Universal indicator initially turns red due to HCl (H+ ions = acidic) then turns colourless as chlorine (I) acid bleaches it.

Question 13

Chlorine + water reaction

Answer 13

Cl2 (g) + H2O(l) ⇌ HCL (aq) + HClO (aq)

Cl2 (g) + H2O (l) ⇌ 2H+ (aq) + Cl- (aq) + ClO- (aq)

Question 14

Chlorine bubbled through water / sunlight reaction?

Answer 14

2Cl2 + 2H2O ⇌ 4H+ + 4Cl- + O2

Question 15

Chlorine + NaOH equation

Answer 15

Cl2(g) + 2NaOH (aq) —> H2O(l) + NaCl (aq) + NaClO (aq)
Cl2 (g) + 2OH- —> H2O(l) + Cl- (aq) + ClO- (aq)
(Cl- aq = green water)

Question 16

HBr + H2SO4

Answer 16

2HBr(g) + H2SO4(aq) —> Br2(g) + SO2(g) + 2H2O(l)

Redox reaction
Br2 - brown fumes (oxidation)
SO2 - choking odour / colourless gas (reduced)

Question 17

NaI + H2SO4

Answer 17

NaI(s) + H2SO4(aq) —> NaHSO4(s) + NaI(g)

Acid base reaction
Observation - white steamy fume

Question 18

HI + H2SO4

Answer 18

2HI(g) + H2SO4 —> I2(g/s) + SO2(g) + 2H2O(l)

Redox recation
I2 - black solid / purple gas (oxidised)
SO2 - choking odour / colourless gas (reduced)

Question 19

HI + SO2

Answer 19

6HI(g) + SO2(g) —> H2S(g) + 3I2(g/s) + 2H2O(l)

Redox reaction
I2 - black solid / purple base (oxidised)
H2S - bad egg smell / colourless gas (reduced)