Question

Calculate the number of moles in 8 gram of Oxygen gas and number of moles in 52 grams of

helium. (Atomic mass O= 16 u, He= 4 u).​

Answer 1

Given - Atoms and their masses for which number of moles to be calculated.

Find - Number of moles of given atoms.

Solution - Number of moles is calculated by the formula - given mass/molar mass.

Keeping the values in equation-

For Oxygen -

Number of moles - 8/32

Number of moles - 0.25 moles.

For Helium -

Number of moles - 52/4

Number of moles - 13 moles.

Hence, number of moles of given amount of oxygen and helium atom are 0.25 and 13 respectively.

Answer 2

To find:

Number of moles in 8 grams of Oxygen gas and number of moles in 52 grams of helium gas.

Calculation:

General expression for number of moles is as follows:

$\boxed{ \bold{no.\:of\:moles = \dfrac{given \: mass}{molecular \: mass} }}$

For Oxygen gas:

Oxygen gas molecule contains 2 atoms of oxygen. So , its molecular mass will be 16 + 16 = 32 g/mol.

$\: \sf{ = > moles = \dfrac{8}{16 + 16} }$

$\: \sf{ = > moles = \dfrac{8}{32} }$

$\: \sf{ = > moles = \dfrac{1}{4} }$

$\boxed{ \: \sf{ = > moles = 0.25 }}$

For Helium gas:

$\: \sf{ = > moles = \dfrac{52}{4} }$

$\boxed{ \: \sf{ = > moles = 13 \: }}$

HOPE IT HELPS.