Question

The mass of 2 grams of atoms of calcium is:
A.$2\,g$
B.$0.05\,g$
C.$0.5\,g$
D.$80\,g$

Answer 1

We have to understand that one gram atom of any element means the mass of one mole of atoms of the element. We can calculate the grams atoms of calcium using their atomic mass and grams atoms given.

Formula used: We can calculate the mass using the formula,
$Mass = n \times atomic\,mass$
Here, n is the gram atoms.

Complete step by step answer:
We know that one mole is equal to a one-gram atom, which in turn is equal to the molar mass.
$1\,mole = 1\,gram\,\,atom = Molar\,mass$
We know the relative atomic mass of calcium is $40\,gm.$
The mass of one gram atom of calcium=$40\,gm.$
We have to know gram atoms can be calculated using the given mass of the element and the atomic mass of the element.
The gram atoms can be calculated using the formula,
$n = \dfrac{{given\,mass}}{{atomic\,mass}}$
We can rearrange the above formula to calculate the mass. We can obtain the mass by multiplying the gram atoms to the atomic mass. We can rearrange the formula as,
$Mass = n \times atomic\,mass$
Let us now calculate mass for a two-gram atom by substituting the values of gram atoms and atomic mass.
Mass=$n \times atomic\,mass$
Mass=$2 \times 40$
Mass=$80\,g$
The mass of two grams of atoms of calcium is $80\,g.$
$\therefore$Option (D) is correct.

Note:
We have to know that the mass of an atom is atomic mass. The SI unit of mass is kilogram, but it is always expressed as Dalton, which is a non-SI unit. We can calculate the mass of an atom by summing up the number of protons and neutrons and multiplying by one amu. The sum of the masses of protons, neutrons and electrons, which make up the atom, is slightly more than the atomic mass.