Question

How many gram atoms are there in $10$ grams of calcium?

• A. $0.25$ gram atoms, $6.023\times {10}^{-23}$ atoms
• B. $0.25$ gram atoms, $1.50\times {10}^{23}$ atoms
• C. $0.1$ gram atoms, $6.023\times {10}^{23}$ atoms
• D. $0.1$ gram atoms, $1.50\times {10}^{23}$ atoms

Answer 1

Answer: (B)

$0.25$ gram atoms, $1.50\times {10}^{23}$ atoms

Weight of calcium $=10$ g

Atomic weight of calcium $=40$ g/g atom

Number of gram atoms of calcium $=\frac{10g}{40g/gatom}=0.25$ gram atoms.

The Avogadro's number is $6.023\times {10}^{23}$ atoms/ g atom

The number of atoms of calcium $=0.25$ gram atoms $\times 6.023\times {10}^{23}$ atoms/ g atom
$\approx 1.50\times {10}^{23}$ atoms

So, the correct option is $B$