Question

Calculate:
A.Mass of $1.5g$ atoms of calcium.(atomic mass= $40$ )
B.Gram atoms in $12.8g$ of oxygen(atomic mass= $16$ )

Answer 1

Gram atom is defined as the mass of an element which is numerically equal to the atomic weight in grams. One mole is equal to the one gram atom which is equal to molar mass. To calculate the and gram atoms of calcium and oxygen respectively we will use the formula of gram atoms with the help of the atomic masses.

Complete step by step answer:
$1g$ of any atom means $1mole$ of that particular element.
Gram atoms is given by the formula as follows:
Number of gram atoms $= \dfrac{W}{{MW}}$
Where, $W =$ weight of the substance
$MW =$ Molecular weight of the substance.
We will use this formula in order to calculate the mass of calcium and gram atoms in oxygen.

A.Given data:
Atomic mass of calcium$= 40$
Number of atoms of calcium $=1.5g$
To find: mass of calcium $= ?$
Formula to be used: mass $=$ gram atoms $\times$ atomic mass
$1g$atoms of calcium$= 40g$
$\therefore 1.5g$ atoms of calcium $= ?$
Mass of calcium $=$ gram atoms of calcium $\times$ atomic mass of calcium
Substituting the atomic mass of calcium and gram atoms of calcium we get,
Mass of calcium $= \dfrac{{1.5 \times 40}}{1}$
Mass of calcium $= 60g$
Therefore, the mass of $1.5g$ atoms of calcium is $60g$ .
B.Given data:
Mass of oxygen $= 12.8g$
Atomic mass of oxygen $= 16$
To find: gram atoms of oxygen $= ?$
Formula to be used: Gram atom $= \dfrac{{given\; mass}}{{atomic\; mass}}$

Gram atom$= \dfrac{{given\; mass}}{{atomic \;mass}}$
Substituting the mass of oxygen and atomic mass of oxygen values in the above formula we get,
Gram atom $= \dfrac{{12.8}}{{16}}$
Gram atom $= 0.8g$
Therefore, the gram atoms present in $12.8g$ of oxygen is $0.8g$ .

So, the correct answer is Option A.

Note: The molar mass, mass and the number of grams all of them belong to the same category called physical quantities. All of these physical quantities are measured in terms of grams or kilograms only. They are used to denote the mass value of that particular substance or species.