a question in an university entrance exam

Apr 2014
2
0
hello everybody.

i encountered the following question when practising for the medschool entrance exam in italy. i was trying to solve it for hours but i don't know how to get the right answer. hope somebody can help. thanks in advance.


Sodium chloride (relative molecular mass = 58.5) has a solubility of 36.0 g per 100 g of water.
The density of the solution is 1.13 g/ml. Which of the following calculations would give the solubility in moles per litre?

A 36.0 x 1000 x 1.13/(58.5 x 136)
B 36.0 x 1000/(58.5 x 1.13)
C 36.0 x 10 x 1.13/58.5
D 36.0 x 10 x 1.13/(58.5 x 136)
E 36.0 x 10/58.5



i know that A is the right answer. but why?
 
May 2010
491
8
wt fraction of NaCL in solution 36/136
wt of NaCL in a liter of solution =1130 * 36/136
mols of NaCL in a liter of solution.Divide line 2 by 58.5