Question

What volume of 75% alcohol by mass $\left(\right.d=0.8g/cm^{3}\left.\right)$ must be used to prepare 150 cc of 30% alcohol by mass $\left(\right.d=0.9g/cm^{3}\left.\right)$ ?

• A. 44.44 mL
• B. 56.25 mL
• C. 67.5 mL
• D. 33.56 mL

Answer 1

Answer: (C)

$M_{1}V_{1}=M_{2}V_{2}$

$\rho =\frac{W_{r}}{V_{4}}$

$V_{r}=\frac{W_{r}}{\rho }$

$\frac{75}{100}\times V\times 0.8=\frac{30}{100}\times 150\times 0.9$

$V=67.5$ ml