Calculate the number of moles and molecules of ammonia (NH3) gas in a volume 67.2 dm^3 of it measured at STP.

Question

Calculate the number of moles and molecules of ammonia (NH₃) gas in a volume 67.2 dm³ of it measured at STP.

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Salim Ahmed Kawsar · Answer 1 · Feb 05, 2023 15:29:48

Given :

Volume of ammonia at STP = 67.2 dm³

To find :

Number of moles and molecules of ammonia

Formulae :

i. Number of moles of a gas (n) = \(\frac{Volume\,of\,\,a\,gas\,at\,STP}{Molar\,volume\,of\,a\,gas}\)

ii. Number of molecules = Number of moles × 6.022 × 10²³ molecules mol^-1

Calculation :

Molar volume of a gas = 22.4 dm³ mol^-1 at STP.

Number of moles (n) = \(\frac{Volume\,of\,\,a\,gas\,at\,STP}{Molar\,volume\,of\,a\,gas}\)

Number of moles of NH₃ = \(\frac{67.2dm^3}{22.4dm^3\,mol^{-1}}\)

Number of molecules = Number of moles × 6.022 x 10²³ molecules mol^-1

= 3.0 mol × 6022 × 10²³ molecules mol^-1

= 18.066 × 10²³ molecules

∴ Number of moles of ammonia = 3.0 mol

Number of molecules of ammonia = 18.066 × 10²³ molecules.

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