Photo AI
X is a Group II metal - CIE - A-Level Chemistry - Question 36 - 2015 - Paper 1
Question 36
X is a Group II metal. It forms a sulfate which is more soluble than barium sulfate. It forms a hydroxide which is more soluble than calcium hydroxide. What could b... show full transcript
Worked Solution & Example Answer:X is a Group II metal - CIE - A-Level Chemistry - Question 36 - 2015 - Paper 1
Step 1
What could be the identity of X?
Answer
To determine the identity of X, we need to analyze the solubility of the sulfates and hydroxides formed by the metal.
-
Sulfate Solubility: Among Group II metals, barium sulfate (BaSO₄) is known to be very insoluble. The question states that the sulfate of X is more soluble than barium sulfate, which leads us to consider strontium (SrSO₄) and magnesium (MgSO₄), as these sulfates are more soluble compared to barium sulfate.
- Barium sulfate (BaSO₄): Insoluble
- Strontium sulfate (SrSO₄): More soluble than BaSO₄
- Magnesium sulfate (MgSO₄): Very soluble
-
Hydroxide Solubility: Next, the question indicates that X forms a hydroxide which is more soluble than calcium hydroxide (Ca(OH)₂). In Group II, the solubility of hydroxides increases down the group:
- Calcium hydroxide (Ca(OH)₂): Slightly soluble
- Strontium hydroxide (Sr(OH)₂): More soluble than Ca(OH)₂
- Magnesium hydroxide (Mg(OH)₂): Poorly soluble
- Beryllium hydroxide (Be(OH)₂): Amphoteric but generally less soluble compared to calcium hydroxide.
Given these points, both strontium and magnesium form sulfates that are more soluble than barium sulfate. However, only strontium forms a hydroxide that is more soluble than calcium hydroxide. Therefore, the identity of X is likely:
Strontium (Sr).