Question

Calculate the average atomic mass of hydrogen using the following data .

Isotope 1H and 2H has % natural abundance as 99.985 and 0.015 and the molar mass as 1 and 2 respectively.

Answer 1

1H = 99.985%

 

2H = 0.015%

 

This means that a sample of hydrogen will contain 99.985% of 1H and 0.015% of 2H

 

The average mass =[ (1x99.985) + (2x0.015)]/ (99.985 + 0.015)

 

                                 = (99.985 + 0.03)/100

 

                                = 100.015/100

 

                                = 1.00015

Answer 2

Explanation: In this question, we are given two isotopes of Hydrogen.

Mass of isotope $H^{1}$=1amu[/tex]

Mass of isotope $H^{2}$=2amu[/tex]

Fractional abundance of the isotopes can be calculated as:  

$\text{Fractional abundance}=\frac{\% abundance}{100}$

Fractional abundance of isotope $H^{1}=\frac{99.985}{100}=0.99985$

Fractional abundance of isotope $H^{2}=\frac{0.015}{100}=0.00015$

To calculate average atomic mass of an element, we use the formula:

$\text{Average Atomic Mass}=\sum_{i=1}^{n}(\text{Fractional abundance})_i\times (\text{Mass number})_i$

Now, putting the values of abundances and mass numbers of 2 isotopes in above equation, we get

$\text{Average Atomic mass of Hydrogen}=(0.99985\times 1amu)+(0.00015\times 2amu)$

Average Atomic Mass of H = 1.00015 amu