Topic 4: Inorganic Chemistry and the Periodic Table

Question 1

Flame test: Sodium

Answer 1

yellow

Question 2

Flame test: Potassium

Answer 2

lilac

Question 3

Flame test: Calcium

Answer 3

yellow-red

Question 4

Flame test: Barium

Answer 4

pale green

Question 5

Flame test: lithium

Answer 5

red

Question 6

Flame test: strontium

Answer 6

Crimson

Question 7

Flame test: Rubidium

Answer 7

red-violet

Question 8

what observation is made when dilute, aqueous sodium hydroxide is added to aqueous iron (II)

Answer 8

green precipitate

Question 9

what observation is made when dilute, aqueous sodium hydroxide is added to aqueous iron (III)

Answer 9

red brown precipitate

Question 10

what is the test for halides

Answer 10

make a solution of the halide
add dilute nitric acid
add silver nitrate solution
observe colour of precipitate formed

Question 11

colour of precipitate formed by chloride ions

Answer 11

white precipitate

Question 12

colour of precipitate formed by bromide ions

Answer 12

cream precipitate

Question 13

colour of precipitate formed by iodide ions

Answer 13

yellow precipitate

Question 14

after testing for a halide, ammonia solution can be added. describe the observations when dilute ammonia solution is added.

Answer 14

chloride- precipitate dissolves (soluble)
bromide- precipitate partially dissolves (insoluble)
iodide- precipitate doesn’t dissolve (insoluble)

Question 15

after testing for a halide, ammonia solution can be added. describe the observations when concentrated ammonia solution is added.

Answer 15

chloride- precipitate dissolves
bromide precipitate dissolves
iodide- precipitate doesn’t dissolve

Question 16

why does a precipitate form when testing for a halide with aqueous silver nitrate?

Answer 16

solid silver halide forms

Question 17

write an ionic equation between the reaction of a halide and silver nitrate solution

Answer 17

Ag+(aq) + Br−(aq) → AgBr(s)

Question 18

The dilute nitric acid is necessary to avoid a false positive in the presence of another anion. Identify this anion and explain why it would result in a false positive. [2]

Answer 18

Carbonate / CO32− [1] Silver carbonate is insoluble [1]

Question 19

test for sulphate ions

Answer 19

make solutions of sulphate
add dilute hydrochloric acid
add barium chloride solution
white precipitate

Question 20

observations of halides with concentrated sulfuric acid and the reaction products

Answer 20

chloride- steamy fumes (HI)
bromide- steamy fumes, brown vapour (HBr, Br₂, SO₂)
iodide-steamy fumes, purple vapour, black solid, yellow solid (HI, I₂,S, H₂S)

Question 21

in cold dilute alkali bromine disproportionates.

write an ionic equation for this reaction

Answer 21

Br2(aq) + 2OH−(aq) → Br−(aq) + BrO−(aq) + H2O(l)

Question 22

Potassium iodide reacts with concentrated sulphuric acid in two stages, the first of which can be represented by the following equation: KI(s) + H2SO4(l) → HI(g) + KHSO4(s)
i. Write an equation for the next stage of the reaction

Answer 22

8HI + H2SO4 → 4I2 + H2S + 4H2O

Question 23

Test for ammonium ions

Answer 23

Add aqueous sodium hydroxide
(Warm)
Hold damp red litmus paper over tube
Turns blue