Question

Calculate the no of atoms present in one drop of water having mass 1.8g.

Answer 1

Answer:

0.3 Na

Explanation:

0.3 * Na

Answer 2

0.3 $N_A$ atoms are present in one drop of water having a mass of 1.8g.

Explanation:

No. of moles of $H_2O$= $\frac{Weight}{M_w}$

$M_{water}$= 18

Given weight =1.8 g

So the number of moles of water =$\frac{1.8}{18}=0.1$ mole.

The number of molecules of $H_2O$ = $0.1\times N_A$

The number of atoms in 1 molecule of $H_2O$ $=3\ atoms$

Therefore $0.1 N_A$ molecules of water (  $H_2O$) contain =$3\times 0.1$ $N_A$$=0.3N_A$ atoms.

Hence, 0.3 $N_A$ atoms are present in one drop of water having a mass of 1.8g.

Note:

• The Avogadro number can be expressed as the number of elementary particles such as molecules, atoms, and compounds per mole of a substance, and is often given the Avogadro number.

• The Avogadro number or Avogadro constant and its value are given as follows: $6.023\times 10^{23}$.

• It is denoted by $N_A$.

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