Question

How many moles are present in $2.1\times {10}^{24}$ atoms of calcium?

• A. $2.3$
• B. $3.5$
• C. $5.2\times {10}^{22}$
• D. $140$

Answer 1

Answer: (B)

$3.5$

$1mole$ of calcium has $6.023\times {10}^{23}$ atoms.

$1mole\to$ $6.023\times {10}^{23}$

$x\to$ $2.1\times {10}^{24}$

$\Rightarrow x=\frac{21\times {10}^{23}}{6\times {10}^{23}}$ $=3.5moles$

So, $=3.5moles$ are present in $2.1\times {10}^{24}$ atoms.