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What volume of gas is evolved at S.t.p if 2g of calcium trioxocarbonate (IV) is...

Chemistry
JAMB 2004

What volume of gas is evolved at S.t.p if 2g of calcium trioxocarbonate (IV) is added to a solution of hydrochloric acid?
[Ca = 40, C = 12, O = 16, Cl = 35.5, H = 1 Molar volume of a gas at s.t.p = 22.4 dm\(^3\)

  • A. 112 cm3
  • B. 224 cm3
  • C. 448 cm3
  • D. 2240 cm3
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Correct Answer: Option C
Explanation

CaCO\(_3\)(s) + 2HCl(aq) → CaCl\(_2\) + H\(_2\)O(l) + CO\(_2\)


The relative molecular mass of CaCO\(_3\) = 40 + 12 + (16 x 3) = 52 + 48 = 100 ;

Relative molecular mass of CO\(_2\)= 12 + (10 x 2) = 44


From the above equation, 100g of CaCO\(_3\) reacts with 44g of CO\(_2\) at s.t.p. i.e  22.4 dm\(^3\)


2g of CaCO\(_3\) will react with (2 x 22.4)/100 of CO\(_2\) = 0.448 dm\(^3\)


0.448 dm\(^3\) = 0.448 x 1000 = 448cm\(^3\)

Alternatively,

CaCO\(_3\)(s) + 2HCl(aq) → CaCl\(_2\) + H\(_2\)O(l) + CO\(_2\)

 1       :     2                                                 1 

The focus is on  CaCO\(_3\)   and  CO\(_2\) and they are in ratio 1 :  1, hence, we can calculate the number of moles of CaCO\(_3\) and substitute the value for the number of moles of CO\(_2\), since their number of moles will also be the same.

Molar mass of CaCO\(_3\) = Ca + C + O\(_3\) = 40 + 12 + (16 x 3) = 100g/mol

Number of moles of CaCO\(_3\) = \(\frac{mass}{molar mass}\) =  \(\frac{2}{100}\) =  0.02 mole

Number of moles = \(\frac{Volume}{molar volume}\) 

        0.02 = \(\frac{volume}{22.4}\)

        Volume = 0.02 x 22.4 = 0.02 x 22400 = 448 cm\(^3\)

There is an explanation video available below.


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Explanation Video

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