For the first-order reaction, 2 n2o (g) → 2 n2 (g) + o2 (g), what is the concentration of n2o after 3 half-lives if 0.25 mol of n2o is initially placed into a 1.00-l reaction vessel? for the first-order reaction, 2 n2o (g) → 2 n2 (g) + o2 (g), what is the concentration of n2o after 3 half-lives if 0.25 mol of n2o is initially placed into a 1.00-l reaction vessel? 3.1 * 10-2 m 1.2 * 10-1 m 6.2 * 10-2 m 1.6 * 10-2 m

According to that each half-life we lose half of the concentration of N2O so,

Because we start with a concentration of N2O = 0.25 mol

so after one half-life the concentration of N2O decrease to the half 0.25/2

= 12.5 x 10^-2 M

and after two half-lives the concentration of N2O of the one half-life decrease to the half (12.5 x 10^-2) / 2

=6.25 x 10^-2 M

and after three half-lives the concentration of N2O of the two half-lives decrease to the half (6.25x10^-2) / 2

= 3.1 x 10^-2 M

∴ your correct answer is 3.1 x 10^-2 M