# IMAT 2011 Q68 (Chemistry)

This question really confused me. Why do you divide the solubility by the density? Could someone explain how they thought through this? Thank you in advance!!

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

A 36.0 x 10/58.5
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 1000 x 1.13/(58.5 x 136)

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Hi!
This question has also been solved before in one of the posts:)
Get the moles of sodium: M=m/n so n = 36/58.5

Density = m/V so V =m/d = 136/1.13

Convert into litres by multiplying by 1000

We now get that n/V = 36.0 x 1000 x 1.13/(58.5 x 136).
Hope it helps:)

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hey! I have one little question, why is 136 here? I though m= 36, thats why Im a bit confused🤧

Hi!
It’s the total mass of solution (solute + solvent)=36+100=136.

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ohhhh okay! I see now. Thank you soooo much, you are so kind   1 Like