Question

What weight of calcium will contain the same number of atoms as are present in $3.2\text{g}$ of sulfur?

Answer 1

Step 1. Given information

$3.2\text{g}$ of sulfur

Step 2. Calculation of no. of molecules in $3.2\text{g}$ of sulfur

Atomic weight of sulfur is $32\text{g}$.

One gram molecular mass of a gas have $6.022\times {10}^{23}\text{atoms}$.

$32\text{g}$ of sulfur contains $6.022\times {10}^{23}\text{atoms}$

$3.2\text{g}$ of sulfur will contain $\frac{6.022\times {10}^{23}\text{atoms}}{32\text{g}}\text{×3.2 g=6.022}\times {10}^{22}\text{atoms}$

Step 3. Calculation of weight of calcium

Atomic weight of calcium is 40 g.

So, $6.022\times {10}^{23}\text{atoms}$ of calcium have weight $40\text{g}$

$6.022\times {10}^{22}\text{atoms}$ of calcium have weight $\frac{40\text{g}}{6.022\times {10}^{23}\mathrm{atoms}}\times 6.022\times {10}^{22}\text{atoms=4 g}$

Hence, $4\text{g}$ weight of calcium will contain the same number of atoms as are present in $3.2\text{g}$ of sulfur.