Question

What is the (mass) percentage of carbon element in sugar?

Answer 1

The mass percentage is calculated by the help of the molecular formula of the compound. The stoichiometric number of a particular element in a compound represents the parts of the compounds that are actually formed from that element.

Complete Step By Step Answer:
There are different types of simple and complex sugars that can be used to determine the mass percentage of carbon elements in it. The most commonly used sugars like sucrose are disaccharides i.e. contain almost two units of glucose or fructose in it.
For the calculation of mass percentage of carbon, the molecular formula of the sugar must be known. Taking the example of sucrose, the molecular formula is ${C_{12}}{H_{22}}{O_{11}}$ which indicates that one molecule of sugar contains twelve carbon atoms in it.
The total mass of sugar can be represented as its molecular mass which can be calculated as follows:
${\text{mass (}}{C_{12}}{H_{22}}{O_{11}}) = (12 \times 12u) + (22 \times 1u) + (11 \times 16u) = 342u$
The mass contributed by twelve carbon atoms is:
${\text{mass of carbon}} = (12 \times 12u) = 144u$
The mass percentage can be expressed as the ratio of the mass that the twelve carbon atoms contain and the total mass of the sugar molecule which is then multiplied by hundred to.
${\text{mass percentage}} = \dfrac{{{\text{mass of carbon}}}}{{{\text{mass of sugar}}}} \times 100$
${\text{mass percentage}} = \dfrac{{144u}}{{342u}} \times 100 = 42.11\%$
$\Rightarrow$ Thus, the mass percentage of carbon element in sucrose sugar is $42.11\%$ .

Note:
The mass percentage of carbon atoms is subject to change as the type of sugar and its chemical formula changes. A mass percentage of $42.11\%$ indicates that for every hundred grams of sugar, there will always be around forty two grams of carbon in it.