Identification of ions and gases：練習題

Which flame color is observed when a sample containing potassium ions is placed in a Bunsen burner flame?
\( (K^{+}) \)

A student tests an unknown solution by adding dilute nitric acid followed by aqueous silver nitrate. A white precipitate forms.
Which ion is present in the solution?

A student is given an unknown solid. They dissolve it in water and add aqueous sodium hydroxide followed by aluminium foil and warm the mixture gently. A gas is evolved that turns damp red litmus paper blue.
Which ion is identified by this procedure?

Which observation is correct when excess aqueous ammonia is added to a solution containing copper(II) ions \( (Cu^{2+}) \)?

A salt solution is tested.
1. Adding aqueous sodium hydroxide produces a red-brown precipitate.
2. Acidifying with dilute nitric acid followed by aqueous barium nitrate produces a white precipitate.
What is the identity of the salt?

Describe the chemical test and the positive result used to identify hydrogen gas, \(H_2\).

Describe the two reagents added to an aqueous solution to test for the presence of chloride ions, \(Cl^-\), and state the observation for a positive result.

A student tests an unknown solution by adding acidified aqueous potassium manganate(VII). The purple solution turns colorless. Identify the anion present and explain the type of reaction occurring.