Question

calculate the number of molecules present in 1 kg of oxygen

Answer 1

Answer: The number of molecules that are present in given amount of oxygen are $188.1875\times 10^{23}$

Explanation:

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

Given mass of oxygen = 1 kg = 1000 g   (Conversion factor:  1kg = 1000 g)

Molar mass of oxygen = 32 g/mol

Putting values in above equation, we get:

$\text{Moles of oxygen}=\frac{1000g}{32g/mol}=31.25mol$

According to mole concept:

1 mole of a compound contains $6.022\times 10^{23}$ number of molecules.

So, 31.25 moles of oxygen will also contain $31.25\times 6.022\times 10^{23}=188.1875\times 10^{23}$ number of molecules.

Hence, the number of molecules that are present in given amount of oxygen are $188.1875\times 10^{23}$

Answer 2

Answer:

The number of molecules present in 1 kg of oxygen is $18.822 \times 10^{24}$

Explanation:

To find: The number of molecules present in 1 kilogram of oxygen:

1 mole of any element = Avogadro’s number

Avogadro number = $\bold{6.023 \times 10^{23}}$

The molar mass of 1 atom of oxygen= 16 gm

In 1 molecule of oxygen, there are 2 atoms, so the molecular mass of $O_{2}$= 16×2 = 32 gm

So 32 grams of $O_{2}$= $6.023 \times 10^{23}$

We all know that according to basic maths, 1 kg=1000grams

So 1000 grams of $O_{2}$= $(6.023 \times 10^{23}$x1000)÷32

= $188.22 \times 10^{23}$ molecules

= $\bold{18.822 \times 10^{24}}$ molecules