Question

What mass of NH3 will contain same number of molecules as that in 36 grams of H2O?​

Answer 1

Given: Amount of water (H2O) = 36g

To find: Mass of NH3 will contain the same number of molecules as that in 36 grams of H2O

Solution:

$No. of moles=\frac{given mass of the substance}{molar mass of the substance}$

∴ $No. of moles of water = \frac{36}{18}= 2$

Also, No. of molecules = No. of moles x Avogadro's Number

No. of molecules of H₂O = (2 x 6.022 x 10²³) = 12.022 x 10²³

So, No of molecules of NH₃ = 12.022 x 10²³ (Given)

∴No. of moles of NH₃ = 12.022 x 10²³ / 6.022 x 10²³ = 2

Mass of NH₃ = No. of moles of NH₃ x Molar mass of NH₃ = (2 X 17) = 34g

Hence, the mass of NH3 will contain the same number of molecules as that in 36 grams of H2O is 34g.