Question

You need 200 ml of 2M H2S04, but the only supply available is concentrated H2SO4 whose concentration is 18 M. What is the initial volume when you prepare the solution?

Answer 1

Answer:

Here is (one way) how to figure out this kind of problem, explained for future use:

The number of moles in the concentrated solution you add is the same as the number of moles in the final solution: n1 = n2

To get the number of moles, we can multiply our concentration by our volume: C1V1 = C2V2

And rather than having a molar concentration, you have a percent - so the easiest thing is to consider that as a fraction:

C1 = 98% = 0.98

C2 = 1,5% = 0.015

Using this and the known final volume (V2 = 200 ml), you can calculate the volume of concentrated acid to add:

V1 = 3.06 ml

Which is added to (200 - 3.06 =) 196.94 ml of water