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 brown gas and a choking gas are formed when solid potassium bromide reacts with concentrated sulfuric acid.

1. Write a balanced equation for the reaction of bromide ions with sulfuric acid that produces the choking 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 concentrated 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.