Answer to Question #106475 in General Chemistry for Beverlie

Question

1. Given a reaction between an organic molecule, denoted as A, and NaSH, we observe the following observations. Using the observations, write a rate law for the reaction.

(a) The rate triples when the concentration of [A] is tripled and the concentration of [NaSH] is held constant.
(b) The rate is decreased when the concentration of [A] is doubled and the concentration of [NaSH] is cut by a factor of 3.
(c) The rate doubles when the concentration of [A] is cut in half and the concentration of [NaSH] is quadrupled.
(d) The rate increases with an increase in temperature.

Answer 1

From (a), (b), (c) it follows that rate is linear dependent on concentrations of [A] and [NaSH], i.e. reaction order is 1 by both reactants. From (d) it follows that reaction has a positive activation energy (E_a > 0) and obeys the Arrhenius law is:

r = k₀*exp(-E_a/RT)*[A]*[NaSH]

where r - rate, k₀ - pre-exponential factor, R = 8.31 J/(K*mole) - gas constant