Question

how many grams of lactose must be added to 655 grams of water in order to prepare a solution with a percent mass concentration of 10%?

Answer 1

Let m $=$ The mass of lactose

$\frac{m}{655+m}=\frac{10}{100}$

$100m=6550+10m$

$90m=6550$

$m=72.78g$