Question

What is the mass of carbon dioxide if carbon is 12 and oxygen is 16.

• A. 42
• B. 44
• C. 46
• D. 48

Answer 1

The correct option is B

44

Law of conservation of mass:

1. It was given by Antoine Laurent Lavoisier in 1789.
2. According to him during chemical reaction in an isolated system mass can neither be created nor be destroyed it gets transformed from one form of matter to another.
3. Mass of reactants $=$Mass of products
4. Reaction:

$\mathrm{C}\left(\mathrm{s}\right)+{\mathrm{O}}_2\left(\mathrm{g}\right)\stackrel{\mathrm{heat}}{\to }{\mathrm{CO}}_2\left(\mathrm{g}\right)$

Carbon Oxygen Carbon dioxide

Given;$(\mathrm{C}=12\mathrm{amu},\mathrm{O}=16\mathrm{amu})$

Step 1. Calculate the mass of all the elements and compounds involved in a reaction.

i. Mass of $\mathrm{C}$ $=$$12\mathrm{amu}$

ii. Mass of ${\mathrm{O}}_2$ $=$$2\mathrm{x}$ Mass of $\mathrm{O}$

$=$$2$ $+$ $16\mathrm{amu}$

$=$$32\mathrm{amu}$

iii. Mass of ${\mathrm{CO}}_2$ $=$Mass of $\mathrm{C}$ $+$ $2\mathrm{x}$ mass of $\mathrm{O}$

$=$$12$ $+$ $2\mathrm{x}16$

$=$$12$ $+$ $32$

$=$$44\mathrm{amu}$

Step 2. Equate mass of reactants and products.

Mass of reactants $=$Mass of products

Mass of $\mathrm{C}$ $+$Mass of ${\mathrm{O}}_2$ $=$ Mass of ${\mathrm{CO}}_2$

$12\mathrm{amu}$ $+$ $32\mathrm{amu}$ $=$$44\mathrm{amu}$

$44\mathrm{amu}$$=$$44\mathrm{amu}$

Thus, the mass of ${\mathrm{CO}}_2$ is $44\mathrm{amu}$.

The correct answer is option B.