Concentration of aqueous solutions

Exercise 4

    

Calculate the mass of ammonia in $500\;mL$ of a $4.76\% $ solution S, knowing that $\rho_S$ $=$ $0.978\frac{g}{mL}$

$\rho_S$ $=$ $0.978$ $\frac{m_S}{V}$ $=$ $0.978$ $m_S$ $=$ $0.978\cdot 500$ $ =$ $489 g$ $\%_{NH_3}$ $=$ $4.76$ $\frac{m_{NH_3}\cdot 100}{m_S}$ $=$ $4.76$ $m_{NH_3}$ $=$ $\frac{4.76\cdot 489}{100}$ $=$ $2.33 \cdot 10^1g$