Question

1.00 mL of a 3.05 × 10–4 M solution of oleic acid is diluted with 9.00 mL of petroleum ether,
forming solution A. Then 2.00 mL of solution A is diluted with 8.00 mL of petroleum ether, forming solution B. How many grams of oleic acid are 5.00 mL of solution B? (Molar mass for oleic acid = 282 g/mol)

Answer 1

Solution A

$Volume=10ml$

$n=\frac{3.05×10^{-4}}{10^{-3}}=3.05×10^{-7}$ moles

Solution B

$Volume=10ml$

$n=3.05×10^{-7}×\frac{2}{10}=0.61×10^{-7}$

Moles of oleic acid in $5ml$ of Solution $B=0.61×10^{-7}×\frac{5}{10}=0.305×10^{-7}moles$

Mass of oleic acid is $0.305×10^{-7}×282=8.601×10^{-6} g$