Question

How many grams of 40% (w/w) NaOH solution should be added to 600 g of water to obtain

10% (w/w) NaOH solution.

Answer 1

Step-by-step explanation:

One mole of NaOH weighs 40gm.

Now 2M solution of NaOH indicates 2 moles of NaOH in 1 litre of water.

So the above question can now be simplified as …if one litre of water contains 80gm(2 moles) of NaOH, then how many grams of NaOH would 250ml solution of the same contain?

Using unitary method,

1000ml corresponds to 80gm NaOH…

1000/4 ml(250ml) corresponds to 80/4 gm NaOH…

Therefore, for 250ml of 2M NaOH, 20 gm of NaOH needs to be added to water.