Select the reagent that will separate the pairs of ions listed.

1. Ag+ and Al3+

2. Cu2+ and Ca2+

3. Mg2+ and K+

4. Ni2+ and Co2+

a) 6 M HCl

b) H2S, 0.2 M HCl

c) (NH4)2S, pH 8

d) (NH4)2 HPO4 in NH3

e) cannot be separated

1 - a, 2-b, 3-d, 4 - e

Explanation:

- Separated by 6M HCl

Silver and aluminum ions can be separated using the acid, 6M HCl.

- Separated by H₂S

Copper and Calcium ions can be separated by the reagent hydrogen sulfide, H₂S.

- Separated by (NH₄)₂HPO₄ in NH₃

Magnesium and Potassium ions can be separated by the reagent Ammonium hydrogen phosphate in ammonia.

- cannot be separated

Nickel and Cobalt ion cannot be separated by the reagents given at all.