Question

Calculate the number of atoms of sulphur present in $0.5$ moles of ${Na}_2{S}_2{O}_3$:

• A. $62.02\times {10}^{23}$ atoms
• B. $622\times {10}^{23}$ atoms
• C. $6.023\times {10}^{23}$ atoms
• D. $6.02\times {10}^{-23}$ atoms

Answer 1

Answer: (C)

$6.023\times {10}^{23}$ atoms

$1$ mole of $N{a}_2{S}_2{O}_3$ contains Avogadro's number of molecules which is $6.023\times {10}^{23}$ molecules.

$0.5$ mole of $N{a}_2{S}_2{O}_3$ will contain $0.5\times 6.023\times {10}^{23}=3.0115\times {10}^{23}$ molecules.

One molecule of $N{a}_2{S}_2{O}_3$ contains $2S$ atoms.

$3.0115\times {10}^{23}$ molecules of $N{a}_2{S}_2{O}_3$ will contain $2\times 3.0115\times {10}^{23}=6.023\times {10}^{23}$ $S$ atoms.

Hence, option $C$ is correct.