Photo AI
A water sample contains at least one of the following anions at concentrations of 1.0 mol L⁻¹ - HSC - SSCE Chemistry - Question 30 - 2023 - Paper 1
Question 30
A water sample contains at least one of the following anions at concentrations of 1.0 mol L⁻¹. * bromide (Br⁻) * carbonate (CO₃²⁻) Outline a sequence of tests that... show full transcript
Worked Solution & Example Answer:A water sample contains at least one of the following anions at concentrations of 1.0 mol L⁻¹ - HSC - SSCE Chemistry - Question 30 - 2023 - Paper 1
Step 1
Add aqueous nitric acid – bubbles indicate carbonate present
Answer
Adding excess nitric acid to the water sample will result in the formation of bubbles. This observation is an indication that carbonate ions (CO₃²⁻) are present because the acid reacts with the carbonate to produce carbon dioxide gas.
The reaction can be represented by the balanced chemical equation:
ightarrow ext{CO}_2(g) + ext{H}_2O(l)$$Step 2
Add silver nitrate solution – creamy precipitate indicates bromide present
Answer
After confirming the presence of carbonate, proceed by adding silver nitrate (AgNO₃) solution to the original water sample. If a creamy white precipitate forms, this indicates the presence of bromide ions (Br⁻).
The corresponding balanced chemical equation for this reaction is:
ightarrow ext{AgBr}(s)$$