Lab 8A – Qualitative Analysis of Group I Cations

1) Suppose you have a sample containing ions A, B, and C. Then, after adding Reagent X, suppose ion C has precipitated. Where are ions A and B? (1 pt)

2) After centrifugation, what get’s decanted (transferred) to another test-tube and what is the solid-formation at the bottom of the initial test-tube called? (1 pt)

3) Why is this type of test called qualitative analysis and not quantitative? (1 pt)

4) In a solution containing various cations, which cations will 6M hydrochloric acid precipitate? (1 pt)

5) Once the first set of insoluble cations in the solution are separated and removed by centrifugation, hot water will be added to separate the lead-ion (Pb+). Why does the lead-ion solubilize and not silver-ion (Ag+) or mercury-ion (Hg+)?  (1 pt)

6) After centrifugation, the supernatant containing the soluble lead-ion (Pb+) is decanted to another test-tube. How is the presence of lead-ion (Pb+) confirmed? (1 pt)

7) What is added to the test-tube that contains the insoluble silver (Ag+) and mercury (Hg+), in order to separate them? (1 pt)

8) In the separation of the soluble silver (Ag+) and mercury (Hg+), which ion precipitates with the addition of 6M ammonia (NH3)? (1 pt)

9) What happens to the silver-ion (Ag+) with the addition of 6M ammonia (NH3)? (1 pt)

10) After centrifugation, the supernatant containing the soluble silver (Ag+) is decanted to another test-tube. How is the presence of silver-ion (Ag+) confirmed? (1 pt)

Lab 8A – Qualitative Analysis of Group I Cations Answer

1) In the solution

2) Precipitated cation or pellet

3) Because we are not testing for its quantity, just the mere presence only of the ions

4) Ag+, Pb2+, Hg22+ (Group 1 Cations)