Experiment 70

Objective

To identify the presence of silver ions in a sample by observing changes upon the addition of sodium hydroxide.

Introduction

When sodium hydroxide (NaOH) is added to a solution containing silver nitrate (AgNO₃), a white precipitate of silver hydroxide (AgOH) forms initially. Over time, this precipitate converts into a brown-colored silver oxide (Ag₂O), confirming the presence of silver ions.

Reactions:

1.    Formation of silver hydroxide:

AgNO3 + NaOH → AgOH ↓ + NaNO3

2.    Conversion to silver oxide:

2AgOH → Ag2O ↓ + H2O2

Materials

Chemicals:

·       Silver nitrate (AgNO₃)

·       Sodium hydroxide (NaOH)

·       Distilled water

Apparatus

·       Test tube

·       Test tube holder

·       Bunsen burner

Reagents

·       Place 3–4 ml of the silver nitrate sample in a test tube.

·       Prepare a 5% NaOH solution in a 250 ml beaker.

Procedure

1.    Place 3–4 ml of the sample in a test tube.

2.    Add 6–7 ml of NaOH to the sample.

3.    Observe the reaction for the formation of a white precipitate.

4.    Wait a few minutes and observe any color change as the precipitate converts to brown.

Observation

Upon adding NaOH, a white precipitate of AgOH forms initially. Over time, this precipitate turns brown, indicating the formation of Ag₂O and the presence of silver ions.

Questions

1.    What is a silver salt?

2.    What is the purpose of using silver nitrate?

3.    How can silver nitrate be identified?

4.    What happens when NaOH is added to silver nitrate?