Question

calculate no of moles and molecules of NH3 in volume 67.2 dm3 of it measured of STP​

Answer 1

NH3=67.2dm^3

No. Of moles = 67.2 ÷ molar volume

of gas

=67.2÷22.4

=3.0 mol

No. of = 3.0 × avocadro's constant

molecule. = 3.0 × 6.022 × 10^23

= 18.066 × 10^23 molecules

Answer 2

Answer : The number of moles of ammonia gas will be, 3.0 mole and the number of molecules of ammonia gas will be, $1.8\times 10^{24}$

Explanation :

First we have to calculate the moles of ammonia gas.

According to the Avogadro's law, the volume of gas is directly proportional to the number of moles of gas at same pressure and temperature. That means,

$V\propto n$

or,

$\frac{V_1}{V_2}=\frac{n_1}{n_2}$

where,

$V_1$ = initial volume of gas = $67.2dm^3=67.2L$

$V_2$ = final volume of gas at STP = 22.4 L

$n_1$ = initial moles of gas  = ?

$n_2$ = final moles of gas at STP = 1 mole

Now we put all the given values in this formula, we get:

$\frac{67.2L}{22.4L}=\frac{n_1}{1mole}$

$n_1=3.0mole$

The number of moles of ammonia gas will be, 3.0 mole.

Now we have to calculate the number of molecules of ammonia gas.

As, 1 mole of ammonia gas contains $6.022\times 10^{23}$ molecules of ammonia gas

So, 3.0 mole of ammonia gas contains $3.0\times 6.022\times 10^{23}=1.8\times 10^{24}$ molecules of ammonia gas

The number of molecules of ammonia gas will be, $1.8\times 10^{24}$