chemistry : class11 Precipitation by Common Ion : Common ion effect : Equilibrium MCQ Questions and Answers
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Precipitation by Common Ion
MCQ questions and answers.
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MCQ Questions
1. When sodium chloride is added to a saturated solution of silver chloride, what is observed?
A.
More silver chloride dissolves
B.
Silver chloride precipitates
C.
The solution becomes neutral
D.
No change occurs
Correct Answer:
Silver chloride precipitates
Explanation:
Sodium chloride provides chloride ions, which are common ions in the dissolution equilibrium of silver chloride. The increased chloride-ion concentration causes silver chloride to precipitate.
2. Which ion acts as the common ion when sodium sulfate is added to a saturated solution of barium sulfate?
A.
Sodium ion
B.
Barium ion
C.
Sulfate ion
D.
Hydrogen ion
Correct Answer:
Sulfate ion
Explanation:
Barium sulfate contains barium ions and sulfate ions. Sodium sulfate adds sulfate ions, so sulfate is the common ion and promotes precipitation of barium sulfate.
3. Adding sodium fluoride to a saturated solution of calcium fluoride will generally cause:
A.
Precipitation of calcium fluoride
B.
Complete dissolution of calcium fluoride
C.
Formation of sodium metal
D.
No change in calcium fluoride solubility
Correct Answer:
Precipitation of calcium fluoride
Explanation:
Sodium fluoride increases the concentration of fluoride ions, which are common ions in calcium fluoride. This reduces its solubility and causes more calcium fluoride to precipitate.
4. Which salt can cause precipitation of silver chloride from a saturated silver chloride solution by providing a common ion?
A.
Sodium nitrate
B.
Potassium chloride
C.
Sodium hydroxide
D.
Potassium sulfate
Correct Answer:
Potassium chloride
Explanation:
Potassium chloride dissociates to give chloride ions. Chloride is a common ion of silver chloride, so its addition can cause silver chloride to precipitate.
5. The solubility of lead(II) iodide decreases when which substance is added to its saturated solution?
A.
Potassium iodide
B.
Potassium nitrate
C.
Sodium acetate
D.
Ammonium nitrate
Correct Answer:
Potassium iodide
Explanation:
Potassium iodide supplies iodide ions, which are common ions in lead(II) iodide. The increased iodide concentration shifts the dissolution equilibrium toward precipitation.
6. What happens when ammonium chloride is added to a saturated solution of ammonium hexachlorostannate containing chloride ions?
A.
The chloride-containing salt becomes more soluble
B.
The chloride-containing salt precipitates more
C.
All ions are removed from the solution
D.
The solution changes into a gas
Correct Answer:
The chloride-containing salt precipitates more
Explanation:
Ammonium chloride adds chloride ions to the solution. Chloride is a common ion, so the solubility of the sparingly soluble chloride salt decreases and precipitation is promoted.
7. Which added ion promotes precipitation of barium sulfate from a saturated barium sulfate solution?
A.
Nitrate ion
B.
Chloride ion
C.
Sulfate ion
D.
Acetate ion
Correct Answer:
Sulfate ion
Explanation:
Sulfate is one of the ions present in the dissolution equilibrium of barium sulfate. Adding sulfate increases its concentration and causes more barium sulfate to precipitate.
8. If potassium bromide is added to a saturated solution of silver bromide, the amount of silver bromide dissolved will:
A.
Increase
B.
Decrease
C.
Remain unchanged in every case
D.
Turn into silver chloride
Correct Answer:
Decrease
Explanation:
Potassium bromide adds bromide ions, which are common ions of silver bromide. The common ion effect lowers the solubility of silver bromide and promotes precipitation.
9. Which ion should be added to a saturated solution of calcium oxalate to promote precipitation of calcium oxalate?
A.
Oxalate ion
B.
Nitrate ion
C.
Chloride ion
D.
Acetate ion
Correct Answer:
Oxalate ion
Explanation:
Calcium oxalate contains oxalate ions. Adding oxalate increases the concentration of this common ion, decreasing calcium oxalate solubility and causing precipitation.
10. The addition of sodium carbonate to a saturated solution of calcium carbonate causes calcium carbonate to precipitate because sodium carbonate adds:
A.
Calcium ions
B.
Sodium ions
C.
Carbonate ions
D.
Hydrogen ions
Correct Answer:
Carbonate ions
Explanation:
Carbonate ions are common ions in calcium carbonate. Their increased concentration shifts the dissolution equilibrium toward the solid, producing more calcium carbonate precipitate.
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