Solid sodium fluoride reacts with concentrated sulfuric acid to produce hydrogen fluoride gas.

1. Write a balanced chemical equation for this reaction.
2. State the role of the sulfuric acid in this reaction.

A gas with a rotten-egg smell and purple fumes are formed when solid sodium iodide reacts with concentrated sulfuric acid.

1. Write a balanced equation for the reaction of iodide ions with sulfuric acid that produces the rotten-egg smelling gas.
2. State the role of the sulfuric acid in this reaction.

Chlorine reacts with hot, concentrated aqueous sodium hydroxide as shown in the equation: $3{Cl}_2+6NaOH\to {NaClO}_3+5NaCl+3H_{2}O$

1. Determine the oxidation state of chlorine in ${NaClO}_3$ and in $NaCl$.
2. State, in terms of redox, what happens to chlorine in this reaction.

Solution Y contains two different negative ions. To a sample of solution Y in a test tube, a student adds:

• silver nitrate solution
• then an excess of dilute nitric acid
• finally an excess of dilute ammonia solution.

The observations after each addition are recorded in the table below:

1. Give the formulas of D, E, and F.
2. Give an ionic equation to show the formation of E.
3. Give an equation to show the conversion of D into G.