Which row describes the solubility of lead(II) chloride and lead(II) sulfate in water?
| lead(II) chloride | lead(II) sulfate | |
|---|---|---|
| A | soluble | soluble |
| B | soluble | insoluble |
| C | insoluble | soluble |
| D | insoluble | insoluble |
▶️ Answer/Explanation
Ans: D
Solubility rules for lead compounds:
1. Lead(II) chloride (PbCl2):
– Most chlorides are soluble, except those of Ag+, Pb2+, and Hg22+
– Therefore, PbCl2 is insoluble
2. Lead(II) sulfate (PbSO4):
– Most sulfates are soluble, except those of Ba2+, Sr2+, Pb2+, and Ca2+
– Therefore, PbSO4 is insoluble
Thus, both lead(II) chloride and lead(II) sulfate are insoluble in water (option D).
Four steps in the preparation of a soluble salt from a dilute acid and a solid metal oxide are listed.
- Warm the dilute acid.
- Evaporate the solution to half of its volume and allow to cool.
- Add excess metal oxide.
- Filter to remove any unreacted solid.
What is the correct order for these steps?
A) 1 → 2 → 3 → 4
B) 1 → 3 → 4 → 2
C) 3 → 1 → 2 → 4
D) 3 → 4 → 1 → 2
▶️ Answer/Explanation
Ans: B
The correct order for preparing a soluble salt from a dilute acid and solid metal oxide is:
1. First warm the dilute acid to speed up the reaction.
2. Then add excess metal oxide to ensure all the acid reacts.
3. Filter to remove any unreacted solid metal oxide.
4. Finally evaporate the solution to concentrate it and allow crystals to form.
This matches option B: 1 → 3 → 4 → 2.
Which symbol equation represents the reaction between aqueous sodium hydroxide and dilute sulfuric acid?
A) Na₂OH + H₂SO₄ → 2NaSO₄ + H₂O
B) Na(OH)₂ + H₂SO₄ → Na₂SO₄ + 2H₂O
C) 2NaOH + H₂SO₄ → 2NaSO₄ + 2H₂O
D) 2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O
▶️ Answer/Explanation
Ans: D
This is a neutralization reaction between an acid (H₂SO₄) and a base (NaOH).
The correct balanced equation is:
\[ 2NaOH + H_2SO_4 \rightarrow Na_2SO_4 + 2H_2O \]
Key points:
- Sodium hydroxide formula is NaOH (not Na₂OH or Na(OH)₂)
- The sulfate ion is SO₄²⁻, so sodium sulfate is Na₂SO₄ (not NaSO₄)
- The equation must balance for atoms and charge
Option D is the only one that meets all these requirements.
The following steps are done to prepare solid magnesium sulfate.
- filtration
- measurement of 20 cm3 of dilute sulfuric acid using a measuring cylinder
- evaporation
- addition of an excess of solid magnesium carbonate to dilute sulfuric acid
What is the correct order for these steps?
A) 2 → 4 → 3 → 1
B) 2 → 4 → 1 → 3
C) 4 → 2 → 1 → 3
D) 4 → 2 → 3 → 1
▶️ Answer/Explanation
Ans: B
The correct sequence is:
- First measure the acid (step 2)
- Then add excess magnesium carbonate to ensure all acid reacts (step 4)
- Filter to remove the unreacted magnesium carbonate (step 1)
- Evaporate the filtrate to obtain solid magnesium sulfate (step 3)
This gives the order: 2 → 4 → 1 → 3 (Option B). The excess magnesium carbonate ensures complete reaction of the acid and is removed by filtration before evaporation.