Question

a 20% solution of H2SO4 has a density of 1.14 g/mL. calculate the molarity, normality and molality of the solution.

Answer 1

As is often the case there is an assumption to be made that the 20% is w/w (rather than v/v or even w/v). So let us assume that it is w/w. Indeed you should state an assumption like this at the start of any answer.

If we have 1 kg of solution it contains 200 g of H2SO4 which contains

200 g/98 g mol^-1 = 2.04 mole


The volume of the solution is

1000 g / 1.14 g ml^-1 = 877 ml

so the molarity is
2.04 mole/0.877 L = 2.33 M

the mass of solvent is
1000 g-200 g =800 g

The molality will be

2.04 mole/0.800 kg = 2.55 molal

Answer 2

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