Question

question 3 (2 points)
how many atoms of hydrogen are in 1.255 grams of methane (ch4)?
1.177 x 10^22 h atoms
4.709 x 10^22 h atoms
0.3159 h atoms
1.884 x 10^23 h atoms

Explanation:

Step1: Calculate molar mass of $CH_4$

The molar mass of $C$ is approximately $12.01\ g/mol$ and of $H$ is approximately $1.01\ g/mol$. For $CH_4$, molar mass $M = 12.01+4\times1.01=16.05\ g/mol$.

Step2: Calculate moles of $CH_4$

Use the formula $n=\frac{m}{M}$, where $m = 1.255\ g$ and $M = 16.05\ g/mol$. So $n=\frac{1.255}{16.05}\ mol\approx0.0782\ mol$.

Step3: Calculate moles of $H$ atoms

In one - mole of $CH_4$, there are 4 moles of $H$ atoms. So moles of $H$ atoms in $0.0782\ mol$ of $CH_4$ is $n_H=4\times0.0782\ mol = 0.3128\ mol$.

Step4: Calculate number of $H$ atoms

Use Avogadro's number $N_A = 6.022\times10^{23}\ atoms/mol$. The number of $H$ atoms $N=n_H\times N_A=0.3128\times6.022\times10^{23}\ atoms\approx1.884\times 10^{23}\ atoms$.

Answer:

$1.884\times 10^{23}\ H$ atoms