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What mass of 95 \% pure \mathrm{CaCO}_{3} will be required to neutralise

50 \mathrm{~mL}$ of $0.5 \mathrm{MHCl} solution according to the following reaction?

\mathrm{CaCO}_{3(s)}+2 \mathrm{HCl}_\mathrm{{(a q)}} \rightarrow \mathrm{CaCl}_{2(\text { aq })}+\mathrm{CO}_{2(\mathrm{~g})}+2 \mathrm{H}_{2} \mathrm{O}_{(1)}
[Calculate upto second place of decimal point]

Option: 1

1.32 \mathrm{~g}
 


Option: 2

3.65 \mathrm{~g}
 


Option: 3

9.50 \mathrm{~g}


Option: 4

1.25 \mathrm{~g}


Answers (1)

best_answer

Give reaction

\mathrm{CaCO}_{3(s)}+2 \mathrm{HCl}_{\text {(aq) }} \rightarrow \mathrm{CaCl}_{2 \text { (aq) }}+\mathrm{CO}_{2}(\mathrm{~g})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l})

From above,

For 2 mole of \mathrm{HCl} = 1 mole of  required

\mathrm{1\; mole\; of\; \mathrm{HCl}=\frac{1}{2}\; mole\; of \;\mathrm{CaCO}_{3}}\\

(50 \mathrm{ml} \times 0.5 \mathrm{M}) \mathrm{HCl}=\frac{50 \times 0.5}{2} \mathrm{m\;mole}\; \mathrm{of}\; \mathrm{CaCO}_{3}\\

                                     \mathrm{=12.5 m\;mole\; of \;\mathrm{CaCO}_{3}}\\

                                     =12.5 \times 10^{-3} \times 100

                                     \mathrm{=1.25 \mathrm{~g}\; of\; \mathrm{CaCO}_{3}} required

For some of \mathrm{0.5M\;HCl} solution \mathrm{1.25g} of \mathrm{CaCO_{3}} required

But \mathrm{CaCO_{3}} is \mathrm{85%} so,

\mathrm{FaCO}_{3}\mathrm{{\;is \;95 \%\;so}},

\mathrm{\% \text { Purity } =\frac{\text { mass of pure }CaCO_{3}}{\text { Total Mass of impure } CaCO_{3}} \times 100} \\

\mathrm{95 =\frac{1.25}{x} \mathrm{~g}} \\

\mathrm{x =\frac{1.25}{95} \mathrm{~g}=1.32 \mathrm{~g}}

Hence the correct option is 1.

Posted by

Gunjita

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