What are the molality, molarity and mole fraction of a solution in which 10% of HCL dissolve in water whose density is 200-gram centimeter cube?

Answer 1

The question should define if it is 10% by mass or 10% by volume HCl. I'll assume 10% by mass which means 10 g HCl/100 ml solution.

To find molarity (M), we want to get moles HCl/liters of solution.

moles HCl = 10 g HCl x 1 mol/36.5 g = 0.274 moles

liters of solution = 100 ml x 1 L/1000 ml = 0.1 liters

M = 0.274 moles/0.100 L = 2.74 M

To find molality (m), we want to get moles HCl/kg of water.

The density given is not a correct value. Again, I'll make the assumption that it is supposed to read 2.00g/cm³, which also probably isn't a correct value as it seems much too high. But the approach will show you how to do the problem using the correct density. So, the answer will not be a valid one since the density is incorrect.

For 1000 ml (1 L) you have 1000 ml x 2.00 g/ml =2000 g of solution

Of that, 100 g is HCl (because you have 10 g HCl/100 ml defined as 10%)

So, grams of water = 2000 g - 100 g = 1900 g water = 1.9 kg water

molality = m = 0.274 moles/1.9 kg = 0.144 m