Question

Which of the following has the highest mass?
(a)- 50 g of iron
(b)- 5 moles of nitrogen gas
(c)- 1 g atom of silver
(d)- $5\text{ x 1}{{\text{0}}^{23}}$ atoms of carbon

Answer 1

Hint For converting moles into a mass, multiply the number of moles given to the molar mass of one atom or one molecule. If you want to convert a number of atoms to the mass then multiply the given number of atoms to the molar mass and then divide it by the Avogadro number.

Complete answer:
Let us study all the options one by one:
(a)- 50 g of iron: In this option, the mass of the iron is directly given which is equal to 50 grams.
(b)- 5 moles of nitrogen gas: For converting moles into the mass, multiply the number of moles given to the molar mass of one atom or one molecule. So, nitrogen gas is a molecule that is formed by two nitrogen atoms therefore, its formula is ${{N}_{2}}$ and its molecular mass is 28 gram. The mass of 5 moles will be:
$5\text{ x 28 = 112}$
The mass of 5 moles of nitrogen gas is 112 grams.
(c)- 1 g atom of silver: 1 g atom means 1 mole of the element, so 1 g atom of the silver means there is 1 mole of silver atom. We know that the atomic mass of silver is 108 g and the mass of 1 mole of silver will be 108 grams.
(d)- $5\text{ x 1}{{\text{0}}^{23}}$ atoms of carbon: If you want to convert number of atoms to the mass then multiply the given number of atoms to the molar mass and then divide it by Avogadro number. The atomic mass of carbon atoms is 12 gram /mol and the value of Avogadro number is $6.023\text{ x 1}{{\text{0}}^{23}}$. So, the mass will be:
$\dfrac{5\text{ x 1}{{\text{0}}^{23}}\text{ x 12}}{6.023\text{ x 1}{{\text{0}}^{23}}}=10\text{ g}$

So, from the above discussion we can see that the option (b) has the highest mass.

Note: Don’t get confused that the formula of nitrogen gas is N, in gaseous form the nitrogen is in molecular form. Avogadro number is the number of atoms present in 1 gram or 1 mole of the element or compound.