64 g of a mixture of NaCl and KCl were treated with concentrated sulphuric acid. The total mass of the metal sulphates obtained was found to be 76 g. What is the mass percent of NaCl in the mixture?

(Molar mass of KCl =74.5 $g m o l^{- 1}$ ,
NaCl = 58.5 $g m o l^{- 1}$ ,
Molar mass of $N a_{2} S O_{4}$ =142 $g m o l^{- 1}$ and Molar mass of $K_{2} S O_{4}$ = 174 $g m o l^{- 1}$

$N a C l + H_{2} S O_{4} \to N a_{2} S O_{4} + H C l K C l + H_{2} S O_{4} \to K_{2} S O_{4} + H C l$

42.85%

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84.91%

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31.50%

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63.17%

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Solution

The correct option is A 42.85%
Consider the mass of NaCl to be x g.
Moles of NaCl = $\frac{x}{58.5}$ and moles of KCl = $\frac{64 - x}{74.5}$
Applying the principle of atom conservation (POAC) to Na,
Moles of sodium in NaCl = moles of sodium in $N a_{2} S O_{4}$
1 $\times$ moles of NaCl = 2 $\times$ moles of $N a_{2} S O_{4}$
Moles of $N a_{2} S O_{4}$ = $\frac{1}{2} \times moles of NaCl$
Applying the principle of atom conservation (POAC) to K,
Moles of potassium in KCl = moles of potassium in $K_{2} S O_{4}$
1 $\times$ moles of KCl = 2 $\times$ moles of $K_{2} S O_{4}$
Moles of $K_{2} S O_{4}$ = $\frac{1}{2} \times moles of KCl$
Total weight of $N a_{2} S O_{4}$ and $K_{2} S O_{4}$ is 76 g
Hence,
$\frac{1}{2} \times \frac{x}{58.5} \times 142 + \frac{1}{2} \times \frac{64 - x}{74.5} \times 174 = 76$
1.214x + 74.738 - 1.168x = 76
0.046x = 1.262
x = 27.43 g
% mass of NaCl = $\frac{27.43}{64} \times 100 = 42.85 %$

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Similar questions

Q. 64 g of a mixture of NaCl and KCl were treated with concentrated sulphuric acid. The total mass of the metal sulphates obtained was found to be 76 g. What is the mass percent of NaCl in the mixture?

(Molar mass of KCl =74.5

g m o l^{- 1}

,
NaCl = 58.5

g m o l^{- 1}

,
Molar mass of

N a_{2} S O_{4}

=142

g m o l^{- 1}

and Molar mass of

K_{2} S O_{4}

= 174

g m o l^{- 1}

N a C l + H_{2} S O_{4} \to N a_{2} S O_{4} + H C l K C l + H_{2} S O_{4} \to K_{2} S O_{4} + H C l

64 g

of a mixture of

N a C l

and

K C l

were treated with concentrated sulphuric acid. The total mass of metal sulphates obtained was found to be %

76 g

. What are the mass percents of

N a C l

in the mixture. The reactions are

2 N a C l + H_{2} S O_{4} \to N a_{2} S O_{4} + 2 H C l

;

2 K C l + H_{2} S O_{4} \to K_{2} S O_{4} + 2 H C l

;

Find the mass of $K N O_{3}$ required to produce 126 kg of nitric acid. Find whether a larger or smaller mass of $N a N O_{3}$ is required for the same purpose.
$K N O_{3} + H_{2} S O_{4} \to K H S O_{4} + H N O_{3} N a N O_{3} + H_{2} S O_{4} \Rightarrow N a H S O_{4} + H N O_{3}$