Question

Find (a) the total number and (b) the total mass of protons in 34 mg of NH₃ at STP. Will the answer change if the temperature and pressure are changed?

Answer 1

(a) 1 mole of NH₃ = {1(14) + 3(1)} g of NH₃

= 17 g of NH₃

= 6.022× 10²³ molecules of NH₃

Total number of protons present in 1 molecule of NH₃

= {1(7) + 3(1)}

= 10

Number of protons in 6.023 × 10²³ molecules of NH₃

= (6.023 × 10²³) (10)

= 6.023 × 10²⁴

⇒ 17 g of NH₃ contains (6.023 × 10²⁴) protons.

Number of protons in 34 mg of NH³

`= (6.022 xx 10^24 xx 34 " mg")/(17000 " mg")`

= 1.2046 × 10²²

(b) Mass of one proton = 1.67493 × 10^–27 kg

Total mass of protons in 34 mg of NH₃

= (1.67493 × 10^–27 kg) (1.2046 × 10²²)

= 2.0176 × 10^–5 kg

The number of protons, electrons, and neutrons in an atom is independent of temperature and pressure conditions. Hence, the obtained values will remain unchanged if the temperature and pressure is changed