Calculate the amount of solute needed to make each of the solution:
225g of 10% (m/m) K2CO3 solution
.50kg of a 18% (m/m) KOH solution
10% w/w(m/m) means 10 g K2CO3 in 100 g solution. You want 225 g soln; therefore,
10g x (225/100) = 22.5 g K2CO3. If we did this right it should be 10%. Let's try it.
(gsolute/gsoln)100 = %
(22.5 g K2CO3/225 g soln)*100 = 10% K2CO3