Question

Calculate the percentage composition of hydrogen in ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\left[\mathrm{C}=12,\mathrm{H}=1,\mathrm{O}=16\right]$.

Answer 1

Step 1: Given information

• The given compound is ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$ (glucose).
• The mass of the Carbon $\left(\mathrm{C}\right)$ element$=12\mathrm{g}$
• The mass of the Hydrogen $\left(\mathrm{H}\right)$ element$=1\mathrm{g}$
• The mass of the Oxygen $\left(\mathrm{O}\right)$ element$=16\mathrm{g}$

Step 2: Calculate the molecular mass of ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$

• To determine the molecular mass, multiply the number of atoms by the mass of that element and sum the masses of all the elements of the compound.
• The molecular mass of ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$ is manipulated as follows:

$$\begin{gathered} \mathrm{Molecular}\mathrm{mass}\mathrm{of}{\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6=12\mathrm{g}\times 6+1\mathrm{g}\times 12+16\mathrm{g}\times 6 \\ =180\mathrm{g} \end{gathered}$$

Step 3: Calculation of percentage composition

• Use the following formula to calculate the percentage composition of hydrogen.

$\mathrm{Percentage}\mathrm{composition}\mathrm{by}\mathrm{mass}=\frac{\mathrm{Mass}\mathrm{of}\mathrm{the}\mathrm{element}\mathrm{in}\mathrm{one}\mathrm{molecule}\mathrm{of}\mathrm{a}\mathrm{compound}}{\mathrm{Gram}\mathrm{molecular}\mathrm{mass}\mathrm{of}\mathrm{the}\mathrm{compound}}\times 100\mathrm{g}$

Step 4: Calculate the percentage composition of Hydrogen:

• $180\mathrm{g}$ of ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$ contains $1\mathrm{g}\times 12=12\mathrm{g}$ of Hydrogen.
• Therefore, $100\mathrm{g}$ ${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$ will contain $\frac{12\mathrm{g}}{180\mathrm{g}}\times 100\mathrm{g}=6.67\mathrm{g}$ Hydrogen.

Thus, the required percentage of hydrogen is $6.67\%$.