Glucose $\left({\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\right)$ contains ______ percentage carbon by weight.

The percent by weight:

• It is also referred to as mass percent composition and is expressed as w/w% meaning weight by weight.
• It is defined as the ratio of the mass of a solute and the mass of the solution multiplied by$100$.

Step 1: Given data

• The total molecular weight of glucose (${\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6$) is $180$g/mol with carbon, hydrogen, and oxygen contributing$72$, $12$ and $96$ g/mol respectively.

Step 2: Use the formula

• Use percent by weight formula i.e. W/W%
• where the mass of solute is the total mass of all the carbon atoms present in glucose and the mass of solvent equals the mass of glucose.
• Mass due to carbon = g/mol.
• Therefore, percentage carbon by weight = $\frac{72}{180}\times 100$= $40\%$

Thus, Glucose $\left({\mathrm{C}}_6{\mathrm{H}}_{12}{\mathrm{O}}_6\right)$ contains $\mathbf{40}$ percentage carbon by weight.