# Question 4013a

Sep 15, 2015

$3 , 0115 \times {10}^{26}$

#### Explanation:

Number of moles of hydrogen present is $n = \frac{m}{M r} = \frac{1000 g}{2 g / m o l} = 500 m o l$
Note that the molar mass of hydrogen is 2g/mol since it is diatomic in nature.
Hence, to find number of molecules present, we must multiply the number of moles by the Avogadro constant which is the number of particles per mole.
ie $n \times {N}_{A} = 500 \times 6 , 023 \times {10}^{23} = 3 , 0115 \times {10}^{26}$

Sep 15, 2015

$3.011 \times {10}^{26}$ molecules

#### Explanation:

To figure out the number of molecules of hydrogen in 1.0 kg of hydrogen gas we need first to find the number of mole ($n$), then:

$\text{no. of molecules" = "no. of moles" xx "Avogadro's number}$

the number of mole n = $\frac{m}{\text{MM}}$, where MM is the molar mass which is equal to 2.0 g/mol. And m = 1 kg = 1000 g.

Therefore,

$n = \frac{1000}{\text{2.0" = "500 mol" = 5.0 xx 10^2 "mol}}$

Therefore,

"no. of molecules" = 5.0 xx 10^2 cancel("mol") xx 6.022 xx 10^(23)"molecules"/cancel("mol")#

$\text{no. of molecules" = 3.011 xx 10^(26) "molecules}$