Question

A student designs an experiment to test substances X, Y, and Z, to determine which one is a catalyst for the reaction: A + B ® C. Only one of the unknown substances is a catalyst, and the others are nonreactive with A, B, or C. When 10 mL of A is added to 10 mL of B, the reaction takes twenty seconds. Bubbles form when the product C is created. The student prepares three test tubes, each containing both reactants A and B. She adds unknowns X, Y, and Z to test tubes 1, 2, and 3, respectively. She then times the reaction in each test tube from the point when the unknown is added until bubbling stops. How can the student identify the catalyst? The test tube that stops bubbling first contains the catalyst. The test tube that produces the most bubbles contains the catalyst. The test tube that bubbles the longest contains the catalyst. The test tube that does not bubble contains the catalyst.

Answer 1

The effect of a catalyst is to increase the speed of the reaction, this is the speed at which reactants, A and B, are consumed, ant the product, C, is produced.


Given that when C is produced the solution bubbles, the bubbles are an indication of progression of the reaction.


The greater the speed of reaction, the earlier the reaction will end and the earlier the bubbles will stop.   


So the student can identify the catalyst because the bubbles will stop first.


Answer: The test tube that stops bubbling first contains the catalyst.