Question

To soften cloths in the wash it is recommended to use 2.0 g of sodium borate per liter of water. If a filled washing machine holds 10 L of water and the correct amount of sodium borate per liter is added, what is the concentration in percent mass/volume of the solution?

Answer 1

% m/v of the solution = 0.2%m/v

Further explanation

$\tt Percent~m/v=\dfrac{mass~solute(g)}{volume~solution(ml)}\times 100\%$

or

% m/v = g solute / 100 ml solution

Concentration : 2 g sodium borate / L water

For 10 L⇒20 g Sodium borate

$\tt \%m/v=\dfrac{20~g}{10,000~ml}\times 100\%\\\\\%m/v=0.2\%$