Question

Which of the following would weigh the highest?

• A. 0.2 mole of sucrose $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$
• B. 2 moles of ${\mathrm{CO}}_2$
• C. 2 moles of ${\mathrm{CaCO}}_3$
• D. 10 moles of ${\mathrm{H}}_2\mathrm{O}$

Answer 1

The correct option is C

2 moles of ${\mathrm{CaCO}}_3$

Step 1: Formula for the mass of a substance

A matter contains numerous atoms and molecules. It can be represented by a unit mole. A mole is a unit to measure the number of atoms and molecules in matter. The molar mass of a substance is considered one mole of that substance.

Mass of the substance = Molar mass of the substance x Number of moles

Step 2: Finding the mass for each substance:

Option A: 0.2 moles of sucrose $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$

The molar mass of sucrose $\left({\mathrm{C}}_{12}{\mathrm{H}}_{22}{\mathrm{O}}_{11}\right)$= 342 g/mol

$\begin{array}{rcl}\mathrm{Mass}\mathrm{of}\mathrm{the}\mathrm{sucrose}& =& \mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{the}\mathrm{sucrose}\times \mathrm{Number}\mathrm{of}\mathrm{moles}\\ & =& 342\mathrm{g}/\mathrm{mol}\times 0.2\mathrm{mol}\\ & =& 68.4\mathrm{g}\end{array}$

Option B: 2 moles of ${\mathrm{CO}}_2$

The molar mass of ${\mathrm{CO}}_2$= 44 g/mol

$\begin{array}{rcl}\mathrm{Mass}\mathrm{of}\mathrm{the}{\mathrm{CO}}_2& =& \mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{the}{\mathrm{CO}}_2\times \mathrm{Number}\mathrm{of}\mathrm{moles}\\ & =& 44\mathrm{g}/\mathrm{mol}\times 2\mathrm{mol}\\ & =& 88\mathrm{g}\end{array}$

Option C: 2 moles of ${\mathrm{CaCO}}_3$

The molar mass of ${\mathrm{CaCO}}_3$= 100 g/mol

$\begin{array}{rcl}\mathrm{Mass}\mathrm{of}\mathrm{the}{\mathrm{CaCO}}_3& =& \mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{the}{\mathrm{CaCO}}_3\times \mathrm{Number}\mathrm{of}\mathrm{moles}\\ & =& 100\mathrm{g}/\mathrm{mol}\times 2\mathrm{mol}\\ & =& 200\mathrm{g}\end{array}$

Option D: 10 moles of ${\mathrm{H}}_2\mathrm{O}$

The molar mass of ${\mathrm{H}}_2\mathrm{O}$= 18 g/mol

$\begin{array}{rcl}\mathrm{Mass}\mathrm{of}\mathrm{the}{\mathrm{H}}_2\mathrm{O}& =& \mathrm{Molar}\mathrm{mass}\mathrm{of}\mathrm{the}{\mathrm{H}}_2\mathrm{O}\times \mathrm{Number}\mathrm{of}\mathrm{moles}\\ & =& 18\mathrm{g}/\mathrm{mol}\times 10\mathrm{mol}\\ & =& 180\mathrm{g}\end{array}$

Among all the substances, 2 moles of Calcium carbonate $\left({\mathrm{CaCO}}_3\right)$ weighs the highest.

Hence, Option C is the correct answer.