Question

Consider the following reaction: \[ {Ca + 2HCl → CaCl2 + H2} \] If \(14\,\text{g}\) of calcium reacts with excess \( {HCl} \), choose the {incorrect} option.

• A. Mass of \( {CaCl2} \) produced is \(38.85\,\text{g}\)
• B. Moles of \( {H2} \) produced is \(0.35\,\text{mol}\)
• C. Volume of \( {H2} \) produced at STP is \(7.84\,\text{L}\)
• D. Mass of \( {CaCl2} \) produced is \(3.885\,\text{g}\)

Hint:

For stoichiometry problems:
Convert given mass into moles first
Use mole ratios from balanced equation
At STP, \(1\) mole of any gas occupies \(22.4\,\text{L}\)

Answer 1

The Correct Option is D

To solve this problem, we need to calculate how much product and by-products are formed when \(14\,\text{g}\) of calcium reacts with excess \( \text{HCl} \).

1. The balanced chemical reaction is: \({Ca} + 2\text{HCl} → {CaCl_2} + \text{H}_2\)
2. Calculate the molar mass of calcium \((Ca)\): \(40.08\,\text{g/mol}\). 
3. Calculate moles of calcium: \(\frac{14\,\text{g}}{40.08\,\text{g/mol}} ≈ 0.349\,\text{mol}\).
4. Using the stoichiometry of the reaction, 1 mole of \( \text{Ca} \) produces 1 mole of \(\text{CaCl}_2\) and 1 mole of \(\text{H}_2\). Thus, \(0.349\,\text{mol}\) of \( \text{Ca} \) will produce:
   • \(0.349\,\text{mol}\) of \(\text{CaCl}_2\)
   • \(0.349\,\text{mol}\) of \(\text{H}_2\)
5. Calculate the mass of \( \text{CaCl}_2 \) produced: \({CaCl_2}\) has a molar mass of \(111.0\,\text{g/mol}\). Hence, \(0.349\,\text{mol} \times 111.0\,\text{g/mol} ≈ 38.74\,\text{g}\).
6. Calculate the volume of \( \text{H}_2 \) at STP (Standard Temperature and Pressure): \(1\,\text{mol}\) of gas at STP occupies \(22.4\,\text{L}\). Therefore, \(0.349\,\text{mol} \times 22.4\,\text{L/mol} ≈ 7.82\,\text{L}\).

Now, let's verify the options:

• Mass of \( \text{CaCl}_2 \) produced is \(38.85\,\text{g}\): Incorrect, calculated mass is approximately \(38.74\,\text{g}\).
• Moles of \( \text{H}_2 \) produced is \(0.35\,\text{mol}\): Correct, because the calculated moles are approximately \(0.349\,\text{mol}\).
• Volume of \( \text{H}_2 \) produced at STP is \(7.84\,\text{L}\): Correct, as calculated volume is approximately \(7.82\,\text{L}\).
• Mass of \( \text{CaCl}_2 \) produced is \(3.885\,\text{g}\): Incorrect, this mass is highly underestimated.

The incorrect options, based on our calculations, are clearly related to the mass of \(\text{CaCl}_2\) produced. Therefore, the correct answer is the option stating the mass of \(\text{CaCl}_2\) as \(3.885\,\text{g}\), which is a significant error compared to the calculated value.