Question

a researcher is designing a laboratory experiment to determine whether the inorganic substance a affects the rate of a reaction between two colored liquids, x and y. when the reaction is complete, the liquid is clear. the reaction between x and y is similar to one used by manufacturers to produce certain chemicals in factories. which method would best answer his question about reaction rate and what will he find out about substance a?
first, he should measure the final temperature of the liquid when x and y react without substance a. then, he should measure the final temperature when he adds substance a to x and y. he will find out if substance a is a catalyst.
first, he should measure how long it takes for the liquid to become clear if x and y are mixed together. then, he should measure how long it takes if he also adds substance a to x and y. he will find out if substance a is a catalyst.
first, he should measure the final temperature of the liquid when x and y react without substance a. then, he should measure the final temperature when he adds substance a to x and y. he will find out if substance a is an enzyme.
first, he should measure how long it takes for the liquid to become clear if x and y are mixed together. then, he should measure how long it takes if he also adds substance a to x and y. he will find out if substance a is an enzyme.

Explanation:

To determine the effect of substance A on the reaction rate between X and Y (which becomes clear when complete), we need to measure the time taken for the liquid to clear (as reaction rate relates to time for completion). Catalysts (inorganic, like substance A) speed up reactions; enzymes are organic, so substance A can't be an enzyme. The correct method measures time to clear with and without A to check if A is a catalyst.

• Option 1: Measures temperature, not reaction rate (time to clear), so incorrect.
• Option 2: Measures time to clear (reaction rate) with and without A, and checks if A is a catalyst (inorganic, so plausible).
• Option 3: Measures temperature (not rate) and claims to find if A is an enzyme (A is inorganic, enzymes are organic), incorrect.
• Option 4: Claims to find if A is an enzyme (inorganic, so wrong) and measures time, but the enzyme claim is invalid.

Answer:

B. First, he should measure how long it takes for the liquid to become clear if X and Y are mixed together. Then, he should measure how long it takes if he also adds substance A to X and Y. He will find out if substance A is a catalyst.