Qualitative inorganic analysis

Question 1

Hydroxides trend down group 2

Answer 1

Solubility increases down the grouo

Question 2

Carbonates trend down group 2

Answer 2

No trend

Question 3

Sulphates trend down group 2

Answer 3

Solubility decreases down group 2

Question 4

Test to identify ammonium

Answer 4

NaOH, gently heat, hold damp red litmus over
Production of ammonia gas, litmus turns blue

Question 5

Test to identify carbonate

Answer 5

HCl/H2SO4, test gas with calcium hydroxide solution (limewater)
Effervescence, CO2 gas produced, limewater turns cloudy

Question 6

Test to identify sulfate

Answer 6

HCl then barium chloride
Production of white precipitate

Question 7

Test to identify chloride (aq)

Answer 7

Nitric acid, then silver nitrate then add dilute ammonia solution
Production of white precipitate, precipitate dissolves

Question 8

Test to identify chloride (solid)

Answer 8

Add concentrated H2SO4
Production of steamy fumes of HCl

Question 9

Test to identify bromide (aq)

Answer 9

Nitric acid, then silver nitrate then add concentrated ammonia solution
Production of cream precipitate and precipitate dissolves

Question 10

Test to identify bromide (solid)

Answer 10

Add concentrated H2SO4
Production of steamy fumes HBr, and red/brown Br2, and pungent smelling SO2

Question 11

Test to identify iodide (aq)

Answer 11

Nitric acid then silver nitrate then concentrated ammonia solution
Production of pale yellow precipitate and no visible change

Question 12

Test to identify iodide (solid)

Answer 12

Add concentrated H2SO4
Production of steamy fumes of HI, H2S (smells of rotten eggs), black sold iodine and sometimes yellow sold sulfur

Question 13

Test to identify thiosulphate ion

Answer 13

Add sulphuric/hydrochloric acid
Yellow precipitate forms

Question 14

Test to identify lead (II)

Answer 14

Add potassium iodide solution
Bright yellow/canary yellow ppt formed

Question 15

Addition of OH- and then excess OH- to [Cu(H2O)6]2+

Answer 15

Blue precipitate
No visible change

Question 16

Addition of OH- and then excess OH- to [Fe(H2O)6]2+

Answer 16

Green precipitate
No is visible change

Question 17

Addition of OH- and then excess OH- to [Cr(H2O)6]3+

Answer 17

Grey precipitate
Precipitate dissolves forming a green solution

Question 18

How do we go from gdm^-3 to moldm^-3?

Answer 18

To moldm^-3 = multiply by Mr
The other way is divide

Question 19

Factors to consider when using a method, apart from cost

Answer 19

Rate of reaction
Atom economy
Temperature
Catalysts
Formation of side products

Question 20

Why can’t the molar % of each compound be used to find the percentage by mass of each component if the relative molecular mass of each component differs?

Answer 20

If relative molecular masses are different, the number of moles present in the chromatogram is not directly related to the mass of each component