Question

The molecular weight of hydrogen peroxide is $34$. What is the unit of gram molecular weight?
A.${\text{g}}$
B.${\text{mol}}$
C.${\text{gmo}}{{\text{l}}^{ - 1}}$
D.${\text{mol}}{{\text{g}}^{ - 1}}$

Answer 1

Gram molecular weight is defined as the mass of one mole molecules of a substance. It is the mass in grams divided by the number of moles of substance.

Complete step by step solution:
- Atomic mass is defined as the number which indicates how many times the mass of one atom of an element is heavier in comparison to $\dfrac{1}{{12}}{\text{th}}$ of the mass of one atom of carbon $\left( {{{\text{C}}^{12}}} \right)$.
- It is represented in an atomic mass unit or amu where $1{\text{amu}} = 1.67 \times {10^{ - 24}}{\text{g}}$. It is the relative atomic mass and not the actual mass of the atom. Gram atomic mass or mass of one gram atom is when the numerical value of atomic mass of an element is expressed in grams per mole then the value becomes gram atomic mass. For example atomic mass of oxygen is $16{\text{amu}}$ which means mass of one atom of oxygen is $16$ times of $\dfrac{1}{{12}}{\text{th}}$ of the mass of one atom of carbon $\left( {{{\text{C}}^{12}}} \right)$ and gram atomic mass of oxygen is $16{\text{gmo}}{{\text{l}}^{ - 1}}$ which means mass of one mole of oxygen atom weigh $16$ times of $\dfrac{1}{{12}}{\text{th}}$ of the mass of one mole atom of carbon $\left( {{{\text{C}}^{12}}} \right)$.
- Similarly, molecular mass is the number which indicates how many times the mass of one molecule of a substance is heavier than in comparison to $\dfrac{1}{{12}}{\text{th}}$ of the mass of one atom of carbon $\left( {{{\text{C}}^{12}}} \right)$. On the other hand, gram molecular mass or mass of 1 mole molecule is the numerical value of molecular mass of the substance expressed in grams per mole then the value becomes gram molecular mass. For example molecular mass of ozone $\left( {{{\text{O}}_3}} \right)$ is $48{\text{amu}}$ which means one molecule of ozone is $48$ times of $\dfrac{1}{{12}}{\text{th}}$ of the mass of one atom of carbon $\left( {{{\text{C}}^{12}}} \right)$ and gram molecular mass ozone molecule is $48{\text{g}}$ which means one mole of ozone molecule weigh $48$ times of $\dfrac{1}{{12}}{\text{th}}$ of the mass of one mole atom of carbon $\left( {{{\text{C}}^{12}}} \right)$.
- As molecular mass of hydrogen peroxide or mass of one molecule of hydrogen peroxide weigh $34{\text{amu}}$ and mass of one mole molecules of hydrogen peroxide will weigh $34{\text{gmo}}{{\text{l}}^{ - 1}}$.

Thus, the correct option is C.

Note: Actual mass is the mass of one molecule or atom of a substance expressed in grams. For example actual mass of ozone is $48 \times \left( {1.67 \times {{10}^{ - 24}}} \right){\text{g}} = 80.16 \times {10^{ - 24}}{\text{g}}$.