Question

What is the mass of 100 molecules of sucrose?

• A. 5.679 $\times {10}^{-22}$
• B. 5.679 $\times {10}^{-20}$
• C. 5.679 $\times {10}^{-21}$
• D. 5.679 $\times {10}^{-23}$

Answer 1

The correct option is B

5.679 $\times {10}^{-20}$

Molecular formula of Sucrose = ${\text{C}}_{12}{\text{H}}_{22}{\text{O}}_{11}$
Molecular mass of Sucrose = 342 g
Also, 1 mole of Sucrose = $6.022\times {10}^{23}$ molecules of Sucrose

$6.022\times {10}^{23}$ molecules of Sucrose = 342 g
1 molecule of Sucrose = $\frac{342}{6.022\times {10}^{23}}$
100 molecules of Sucrose = $100\times \frac{342}{6.022\times {10}^{23}}$
= 5.679 $\times {10}^{-20}$