Question

1. using dimensional analysis, calculate the mass, in grams, of hydrogen in 43.605 g of h₃po₃.

Explanation:

Step1: Calculate molar mass of $H_3PO_3$

The molar mass of $H$ is approximately $1.008\ g/mol$, $P$ is approximately $30.97\ g/mol$, and $O$ is approximately $16.00\ g/mol$.
$M_{H_3PO_3}=3\times1.008 + 30.97+3\times16.00=81.994\ g/mol$

Step2: Determine mole - ratio of $H$ in $H_3PO_3$

In one molecule of $H_3PO_3$, there are 3 moles of $H$ atoms.

Step3: Calculate moles of $H_3PO_3$

$n_{H_3PO_3}=\frac{m_{H_3PO_3}}{M_{H_3PO_3}}=\frac{43.605\ g}{81.994\ g/mol}\approx0.5318\ mol$

Step4: Calculate moles of $H$

Since there are 3 moles of $H$ for every 1 mole of $H_3PO_3$, $n_H = 3\times n_{H_3PO_3}=3\times0.5318\ mol = 1.5954\ mol$

Step5: Calculate mass of $H$

$m_H=n_H\times M_H=1.5954\ mol\times1.008\ g/mol\approx1.618\ g$

Answer:

$1.618\ g$