Question

Calculate the molar mass of the following: 
(i) \(\text{H}_2\text{O}\) (ii) \(\text{CO}_2\) (iii) \(\text{CH}_4\)

Answer 1

(i) \(\text{H}_2\text{O}\): 
The molecular mass of water, \(\text{H}_2\text{O}\)
\(= (2 \times \text{Atomic mass of hydrogen}) + (1 \times \text{Atomic mass of oxygen})\)
= [2(1.0084) + 1(16.00 u)]
= 18.016
= 18.02 u

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(ii) \(\text{CO}_2\): 
The molecular mass of carbon dioxide, \(\text{CO}_2\)
\(= (1 \times \text{Atomic mass of carbon}) + (2 \times \text{Atomic mass of oxygen})\)
= [1(12.011 u) + 2 (16.00 u)]
= 12.011 u + 32.00 u
= 44.01 u

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(iii) \(\text{CH}_4\): 
The molecular mass of methane, \(\text{CH}_4\)
\(= (1 \times \text{Atomic mass of carbon}) + (4 \times \text{Atomic mass of hydrogen})\)
= [1(12.011 u) + 4 (1.008 u)]
= 12.011 u + 4.032 u
= 16.043 u