This chemistry question involves key chemical concepts and calculations. The detailed solution below walks through each step, from identifying the reaction type to computing the final answer.
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For question 2a, we need to calculate the concentration of a substance after a certain time, given its half-life and initial concentration for a first-order reaction. Step 1: Convert the given time to minutes. The half-life is given in minutes, so we convert the total time from hours to minutes. t = 2.24 h × 60 minh = 134.4 min Step 2: Calculate the rate constant (k) for the first-order reaction. For a first-order reaction, the half-life (t_1/2) is related to the rate constant (k) by the formula: t_1/2 = ((2))/(k) Rearranging to solve for k: k = ((2))/(t_1/2) k = (0.693)/(32 min) k ≈ 0.02166 min^-1 Step 3: Use the integrated rate law for a first-order reaction to find the concentration at time t. The integrated rate law is: ([A]_t) = ([A]_0) - kt Alternatively, in exponential form: [A]_t = [A]_0 e^-kt Where [A]_t is the concentration at time t, and [A]_0 is the initial concentration. Step 4: Substitute the known values into the integrated rate law. [A]_t = (2.7 × 10^10 molecules/L) × e^-(0.02166 min^-1 × 134.4 min) [A]_t = (2.7 × 10^10 molecules/L) × e^-2.9076 [A]_t = (2.7 × 10^10 molecules/L) × 0.05462 [A]_t = 1.47474 × 10^9 molecules/L Step 5: Round the final answer to an appropriate number of significant figures (two significant figures, based on the given data). [A]_t = 1.5 × 10^9 molecules/L That's 2 down. 3 left today — send the next one.