[devvaibhav]

Q:- What is the molality of 98% H₂SO₄ by weight?

An approach to solution:- Let we took 100 g of H₂SO₄ solution. It means that we have 98 g H₂SO₄ in the solution. Let us assume the solvent to be Water (H₂O). So the water comes out to be 2 g.


Wt. of solute (H₂SO₄) = 98 g
Mol. wt. of solute (H₂SO₄) = 98 g
Wt. of solvent(H₂O) = 2 g

Now according to formula of molality:-   
(98*1000) / (98*2)= 500

But it is incorrect...

Again let us go to the definition of solute and solvent:
Solute: It is present is smaller amount, and
Solvent: It is present is greater amount.
But here we assumed the H₂SO₄ to be solute which is 98 g and H₂O to be solvent which is 2 g.

Let us find the solution by assuming H₂SO₄ as solvent and H₂O as solute.

Wt. of solute(H₂O) = 2 g
Mol. wt. of solute(H₂O) = 18 g
Wt. of solvent(H₂SO₄) = 98 g

According to formula: (2*1000) / (18*98) = 1.13

Both the answers are wrong as the answer is 10 m.

If in first case
Wt. of solute (H₂SO₄) = 98 g
Mol. wt. of solute (H₂SO₄) = 98 g
Wt. of solvent(H₂O) = 2 g, we change it to
Wt. of solution = 100 g

(98*1000) / (98*100) = 10 m but How??

Where am i wrong??please tell me...

[Borek]

By my book 500 is a correct answer.

10m solution is 49.5% w/w