# Question ade66

Dec 12, 2014

The answer is $2.15 g$.

A solution's percent concentration by mass is defined as the mass of solute divided by the total mass of the solution and multiplied by 100%.

c= (mass_(solute))/(mass_(solution)) * 100%

Therefore, the mass of solute needed for this solution is

m_(K_2CO_3) = (c * m_(solution))/100 = (5.00% * 43.0)/(100%) = 2.15g#

It is important to try and estimate what that mass could be even before calculating it; this could have been done by takin the $\frac{1}{20}$th part (the equivalent of 5%) of $43 g$, which is roughly $2 g$.