Question

The number of molecules in 27 g water is

Answer 1

★$\color{darkblue}\underline{\underline{\sf Given-}}$

• Weight of water = 27g
• Molecular Weight of water = 18g

★$\color{darkblue}\underline{\underline{\sf To \: Find-}}$

• Number of molecule (N)

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★$\underline{\sf Formula \: Used -}$

$\color{violet}\bullet\underline{\boxed{\sf Mole(n)=\dfrac{Weight}{Molecular \: Weight}}}$

$\color{violet}\bullet\underline{\boxed{\sf No.\:of\: molecule (N)=nN_A}}$

${\sf N_A=Avogadro \: Number = 6.023×10^{23}\:atoms/mol}$

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$\color{darkblue}\underline{\underline{\sf Solution-}}$

$\large\implies{\sf Mole(n)=\dfrac{Mass}{Molecular \: Weight}}$

$\implies{\sf n=\dfrac{27}{18}}$

$\color{orange}\implies{\sf n=1.5}$

$\large\implies{\sf No. \: of \: molecules (N)=n×N_A}$

$\implies{\sf N=1.5×6.023×10^{23}}$

$\color{red}\implies{\sf N=9×10^{23} }$

$\color{darkblue}\underline{\underline{\sf Answer-}}$

★Number of water molecules $\color{red}{\sf 9×10^{23}}$

Answer 2

27 gm of water will have 9.033 × 10²³ molecules.

Given:

The given weight of water is 27 gm.

To Find:

The total number of molecules present in 27 gm of water.

Solution:

Here,

We have,

The weight of the water is 27 gm.

We know, that the molecular weight of water is 18 gm.

We know, that 1 mole of any substance contains Avogadro's number of molecules ($N_{A}$).

At first, we need to find the number of moles present in 27 gm of water.

we know,

Mole (n) = (Weight) / (Molecular weight)

i.e,

n = 27/18

= 1.5

That means, 27 grams of water has 1.5 moles of water.

Then if 1 mole of water contains $N_{A}$ molecules.

Then 1.5 moles of water will contain 1.5 $N_{A}$ molecules.

Again, $N_{A}$ = 6.022 × 10²³

Therefore,

1.5$N_{A}$ = 1.5 × 6.022 × 10²³

= 9.033 × 10²³ molecules.

Thus, 27 gm of water will have 9.033 × 10²³ molecules.

#SPJ3