Question

Nitrous oxide (N2O) is used as an anesthetic (laughing gas) and in aerosol cans to produce whipped cream. It is also a potent greenhouse gas. The decomposition of N2O is first order. It decomposes slowly to N2 and O2:

How many half-lives will it take for the concentration of the N2O to reach 25.00 % of its original concentration?

Answer 1

Solution:-

N / N₀ = (1/2)ⁿ

Where, N = final concentration

N₀ = original concentration

n = number of half-lives.

Let, N₀ = 100%

then, N = 25%

Thus,

(25 / 100) = (1/2)ⁿ

(1/4) = (1/2)ⁿ

(1/2)² = (1/2)ⁿ

n = 2

Hence, the number of half-lives required for the concentration of the N₂O to reach 25% of it's original concentration is = 2

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