Question

35 Mass of one atom of an element is 6.645 x 10-23 g. How many moles of element are
there in 0.320 kg​

Answer 1

$\checkmark$ Given:

Mass of one atom of an element is 6.645 x 10⁻²³ g

$\checkmark$ To Find:

How many moles of element are  there in 0.320 Kg​

$\checkmark$ Solution:

We know that,

$\red{\bigstar \ \boxed{\rm N=\dfrac{m}{M} \times N_{0}}}$

Here,

• N = number of atoms
• m = given mass
• M = molar mass
• N₀ = avogadro number

Finding value of M:

Given that,

Mass of one atom of an element is 6.645 x 10⁻²³ g

Hence,

• N = 1
• m = 6.645 x 10⁻²³ g

We know that,

• N₀ =  6.622 x 10²³ g

Hence,

$\orange{\rm \implies M=\dfrac{m \times N_{0}}{N}}$

Substituting the values,

We get,

$\blue{\rm \implies M=6.645 \times 10^{-23} \times 6.022 \times 10^{23} \ g}$

On further simplification,

We get,

$\green{\rm \implies M \approx 40 \ g}$

According to the question,

We are asked to find how many moles of element are  there in 0.320 Kg​

Hence,

$\red{\bigstar \ \boxed{\rm n= \dfrac{m}{M}}}$

Here,

• n = number of moles
• m = given mass
• M = molar mass

Given that,

How many moles of element are  there in 0.320 kg​

Hence,

• m = 0.320 Kg = 320 g

We found out that,

• M = 40 g

By Substituting the values,

We get,

$\blue{\rm \implies n=\dfrac{320}{40} \ moles}$

On further simplification,

We get,

$\pink{\rm \implies n=8 \ moles}$

Hence,

8 moles of element are  there in 0.320 Kg