[joe900]

the reaction is:
 K₂CO₃ + 2 H₂SO₄ --- 2 KHSO₄ + CO₂ + H₂O

and I have to dissolve 15 g of K2CO3 in 15 ml of water and add two times more than it is theoretically (why??) of 60 % H2SO4.
I have only 96 % H2SO4, how to calculate that?

*(the answer is about 45 ml of acid and 29 ml od water, but i do not know how to calculate)

[Arkcon]

Welcome, caro900: to the Chemical Forums.  According to the Forum Rules{click}, we want to see your attempt.

Try to figure it out theoretically, before you have to address practical concerns.  Assume you had 100% H2SO4, how much would you need to add for a perfect stoichiometric amount?  How much is twice that, since that is how much the method says is needed?  It mention using 60% concentration, what if it asked for 50%, you know how 50% compares to 100%, or how 10% compares to 100%, so you know you can handle any percentage.

[Dan]

the answer is about 45 ml of acid

This is wrong - by factor of 1.84...