Question

How many grams are contained in 1 mole of Na atoms?
(A) 13g
(B) 23g
(C) 1g
(D) \[\dfrac{1}{{23}}\]g

Answer 1

Hint: On multiplying molar mass of the substance to the number of moles provided in the problem, we get the grams of the substance contained in that particular mole of the substance. Atomic weight when multiplied to the number of moles results in its gram weight.

Complete step-by-step solution:
Mole is a standard unit of measurement of an amount of a substance. Substances react in the simple ratios of their moles. One mole consists of Avogadro number of atoms i.e. \[6.022 \times {10^{23}}\] atoms. The amount of atoms in 12.0 grams of Carbon-12 is the same as Avogadro’s number as it is for 1 mole of carbon i.e. a sample of 12 grams of carbon is equal to its one mole. It is similar to a dozen.
The molar mass is the amount of grams present in one mole of a substance. It is also the average atomic weight of a substance. For example, carbon has an atomic weight of 12 amu, so its molar mass is 12 grams per mole. The formula for converting moles to gram is written as-
Grams = moles \[ \times \] atomic weight
We are given 1 mole of sodium atoms
Therefore, grams = 1 mole \[ \times \] atomic weight of sodium atom
Atomic weight of sodium atom is 23 (number of neutrons + number of protons)
\[\therefore \]grams = 1 mole \[ \times \] 23
= 23 grams
Thus, 23 grams are contained in 1 mole of sodium atom.

Hence, the correct option is (B).

Note: Calculating mass like this is known as gram atomic mass. It is the mass of one mole of that element. For example, gram atomic mass of hydrogen is 1 gram for one mole of hydrogen. It is the same as the atomic weight of a hydrogen atom.