Question

Calculate the number of molecules in 8 grams of methane (CH4). Given atomic mass of C =12 u, H =14.

Answer 1

Answer:

The answer is 2

Explanation:

The gram of molecules = 8

The atomic mass of CH4 =16

No. of molecules= Atomic mass/Gram of molecules

=16/8

=2moles.

Answer 2

The number of molecules in 8 grams of methane is $3.011$ × $10^{23}$ molecules.

Given:

Mass of Carbon = 12 u

Mass of Hydrogen = 1 u

To Find:

The number of molecules in 8 grams of methane.

Solution:

We can simply solve this problem by using the following process.

"The molecular mass of an element is the sum of atomic masses of all its constituent elements."

To calculate the number of molecules we use the formula

Number of Molecules = (Number of moles) × ( $6.022$ × $10^{23}$ )

Molar mass of methane = 12 + (4 × 1)

= 16 g/mol

∴ 1 mol of $CH_{4}$ = 16gm

So,

16gm of methane has $6.022$ × $10^{23}$ molecules

Now, 8gm of methane will contain

$6.022$ × $10^{23}$ × $\frac{8}{16}$

= $3.011$ × $10^{23}$ molecules

Hence, the number of molecules in 8 grams of methane is $3.011$ × $10^{23}$ molecules.

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