Question:

Ten grams of calcium carbonate which is only 90% pure is treated with excess hydrochloric acid. What is the mass of $CO_{2}$ gas liberated? (Atomic mass: $Ca=40$, $C=12$ & $O=16$) ________.

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Always calculate based on the pure weight of the reactant.
Updated On: Jun 26, 2026
  • 4.4g
  • 3.96g
  • 2.2g
  • 0.44g
  • 0.22g
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The Correct Option is B

Solution and Explanation

Step 1: Concept
Determine the amount of pure reactant and use stoichiometry.

Step 2: Meaning

Pure $CaCO_3 = 90\% \text{ of } 10g = 9g$. Molar mass of $CaCO_3 = 100g/mol$; Molar mass of $CO_2 = 44g/mol$.

Step 3: Analysis

Reaction: $CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2$. 100g $CaCO_3$ gives 44g $CO_2$. Mass of $CO_2 = \frac{44}{100} \times 9$.

Step 4: Conclusion

Mass $= 3.96g$. Final Answer: (B)
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