Question

Which of the following has maximum mass?
A. $0.1g$ atom of Carbon
B. $0.1$ mol of ammonia
C. $6.02 \times {10^{22}}$ mol of hydrogen
D. $1120cc$ of $C{O_2}$ at STP

Answer 1

Hint: Convert all the standard units to grams. Moles can be converted to mass by multiplying the number of moles given to the molar mass of the one atom/ molecule and to convert the number of atoms to mass multiply the given number of atoms to molar mass and then division of the Avogadro number is done.

Complete answer:
A. $0.1g$ atom of carbon – $0.1g$ atom means $0.1$ moles of the element, so $0.1g$ atom of the carbon means there is 0.1 mole of carbon atom present.
The atomic mass of carbon is $12g$ therefore the mass of 0.1 moles of carbon is $1.2g$
B. $0.1$ mole of $N{H_3}$ - To convert moles into mass, the given number of moles is multiplied by the molar mass of the molecule. So ammonia is formed by a nitrogen atom and 3 hydrogen atoms so the molecular mass of $N{H_3}$ is $17g.$
The mass of $0.1$ moles $N{H_3}$will be $0.1 \times 17 = 1.7g$
C. $6.02 \times {10^{22}}$ mol of ${H_2}$- Conversion of the number of atoms to mass is done by multiplying the given number of atoms to the molar mass and then dividing it by the Avogadro number.
The atomic mass of ${H_2}$ is $2\mu $. The mass of $6.02 \times {10^{22}}$ mol of ${H_2}$ will be $\dfrac{{6.02 \times {{10}^{22}} \times 2}}{{6.023 \times {{10}^{23}}}} = 0.19g$
D. \[1120cc\] of $C{O_2}$ at STP- 1 mole of any gas is equal to \[22.4L\] at STP
So the total number of the mole will be $\dfrac{{1120}}{{22400}}$ (22.4 L is converted to mL)
Weight will be equal to mol multiplied by molecular weight $\dfrac{{1120}}{{22400}} \times 44 = 2.2g$
Therefore the correct answer is option D.

Note:
The molar mass is the mass of a given substance divided by the amount of substance in a given sample of matter. Molar mass is expressed in g/mol. Molecular mass is the mass of a single molecule. Molecular weight and formula weight are commonly used synonyms of molar mass.