Question

The cost of table salt is Rs.2 per kg where as the cost of table sugar is Rs.5 per kg. Calcuate the cost os substances per mole and which is cheaper?

Answer 1

Number of Moles = given /molar mass
Mole of NaCl in 1kg of NaCl = 1000gram/58.8 = 17.24 mols (molar wt of NaCl is 58.8)
Moles of sugar in 1 kg sugar sample is = 1000/342 = 2.92 mols (mol. wt. of cane sugar is 342)
17.24 mol of NaCl cost 2 Rs
∴ 1 mole of NaCl will cost = 2/17.24 = 0.116 Rs.
2.92 moles of sugar cost 5 Rs
∴ 1 mole of sugar cost 5/2.92 = 1.71 Rs.
Sugar is costlier than NaCl.