Question

Find the number of gram atoms in $18$ grams of H${}_2$O

• A. $3$N${}_A$
• B. $3$
• C. $48$H${}_A$
• D. $\frac{3}{N_A}$

Answer 1

The correct option is A $3$N${}_A$

number of moles of $H_{2}O=\frac{18g}{18g/mol}=1mol$

now one mole of water contains $6.022\times {10}^{23}$ molecules.

but, there are three atoms in $H_{2}O$ molecule.

Therefore, number of gram atoms is $3N_a$ where $N_a=6.022\times {10}^{23}$