A certain substance, X, decomposes. 55% of X remains after 110 minutes. How much X remains after 200 minutes if the reaction order with respect to X is zero order?

• A. 45%
• B. 15%
• C. 25%
• D. 35%

Answer: (D)

Verified step by step guidance

1. Identify that the reaction is zero order, which means the rate of reaction is constant and does not depend on the concentration of the reactant.
2. Use the zero-order rate equation: \( [X] = [X]_0 - kt \), where \([X]\) is the concentration at time \(t\), \([X]_0\) is the initial concentration, and \(k\) is the rate constant.
3. Determine the initial concentration \([X]_0\) and the concentration \([X]\) after 110 minutes. Since 55% of X remains, \([X] = 0.55[X]_0\).
4. Calculate the rate constant \(k\) using the equation \( [X] = [X]_0 - kt \) with the known values at 110 minutes.
5. Use the calculated rate constant \(k\) to find the concentration \([X]\) after 200 minutes using the zero-order rate equation.