How much 80% pure salt cake could be produced form 100.0 g of 90% pure salt in the above reaction?
A
43.92 g
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B
68.62 g
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C
87.84 g
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D
136.25 g
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Solution
The correct option is D136.25 g The molar masses of NaCl and Na2SO4 are 58.5 g/mol and 142 g/mol respectively. 100.0 g of 90% pure NaCl corresponds to 100.0×90100×158.4=1.54 moles. The
number of moles of Na2SO4 formed from 1.54 moles
of NaCl are 1.542=0.77 moles. The mass of Na2SO4 obtained is 0.77×142=109.8 g. But the salt cake is 80% pure. Hence, the mass of the salt cake that can be obtained is 109.8×10080=136.25 g.