Question

$5$ moles of $AB_2$ weigh $125 \times 10^{-3}\, kg$ and $10$ moles of $A_2B_2$ weigh $300 \times 10^{-3}\, kg$. What is the sum of molar mass of $A\ (M_A)$ and molar mass of $B (M_B)$ in $g\, mol^{-1}$ ?

Answer 1

Molar mass of $A = 5 \times 10^{-3}$
Molar mass of $B = 10 \times 10^{-3}$
$5$ mol $AB_2$ weighs $125 \,g$
$\therefore AB_2 = 25\, g/mol$
$10$ mol $A_2B_2$ weighs $300 \,g$
$\therefore A_2B_2 = 30 \,g/mol$
$\therefore $ Molar mass of $A(M_A) = 5\, g$
Molar mass of $B (M_B) = 10 \,g$
$\Rightarrow 5 + 10 = 15\,g$