Question

a) 0.6723 g of an organic compound gave on combustion 1.530 g of carbon dioxide and
0.625 g of water. Find the percentage of carbon and hydrogen in the compound.​

Answer 1

Percentage of Carbon in organic compound = 4.6%

percentage of Hydrogen in organic compound = 10.4%

Mass of an organic compound = 0.6723 g

Mass of Carbon dioxide produced on combustion =  1.530 g

Mass of water produced = 0.625 g

Mass of carbon in carbon dioxide  = 12 g in 44 g

44 g of Co₂ contains 12 g

mass of carbon produced = $\frac{mass of carbon in mole of Co_2 \times mass of Co_2 produced}{mass of 1 mole of Co_2}$

= $\frac{12\times 1.530}{44}$

= $\frac{18.36}{44}$

mass of carbon produced = 0.031 g

percentage of carbon in organic compound = $\frac{mass of carbon produced}{mass of organic compound}$

=  $\frac{0.031}{0.6723}\times 100$

= 0.046 ×100

percentage of carbon in organic compound = 4.6 %

mass of Hydrogen produced =  $\frac{mass of hydrogen in mole of H_2O \times mass of H_2O produced}{mass of 1 mole of H_2O}$

= $\frac{2 \times 0.625}{18}$

=$\frac{1.25}{18}$

= 0.0695 g

0.0695 is rounded off to 0.07 g

mass of hydrogen produced = 0.07 g

percentage of Hydrogen in organic compound = $\frac{mass of Hydrogen produced}{mass of organic compound}$

=  $\frac{0.07}{0.6723}\times 100$

=  0.104 ×100

= 10.4 %

percentage of Hydrogen in organic compound =10.4%