A 0.1 mol L^{-1} solution of an unknown salt is to be analysed - HSC - SSCE Chemistry - Question 22 - 2020 - Paper 1
Question 22
A 0.1 mol L^{-1} solution of an unknown salt is to be analysed. The cation is one of magnesium, calcium or barium. The anion is one of chloride, acetate or hydroxide... show full transcript
Worked Solution & Example Answer:A 0.1 mol L^{-1} solution of an unknown salt is to be analysed - HSC - SSCE Chemistry - Question 22 - 2020 - Paper 1
Step 1
Cation Tests: Flame Test
96%
114 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Perform a flame test using a clean wire loop.
If the flame is pale green, the cation is barium.
If the flame is brick red, the cation is calcium.
No color indicates that the cation is magnesium.
Step 2
Anion Test: Add Silver Nitrate
99%
104 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Add a few drops of AgNO₃(aq) to a small sample of the unknown salt solution.
If a white precipitate forms, chloride ions (Cl⁻) are present.
If no precipitate forms, proceed to the next test.
Step 3
Anion Test: Add Universal Indicator
96%
101 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
Test the solution with a universal indicator to determine pH.
If the solution is neutral, it indicates the presence of acetate ions (CH₃COO⁻).
If the solution is basic, it suggests the presence of hydroxide ions (OH⁻).
Step 4
Balanced Chemical Equations
98%
120 rated
Only available for registered users.
Sign up now to view full answer, or log in if you already have an account!
Answer
For the formation of a precipitate with silver nitrate:
ightarrow AgCl(s)$$
2. For the reaction with hydroxide ions:
$$Ca^{2+}(aq) + 2OH^-(aq)
ightarrow Ca(OH)_2(s)$$
