Question

multiple choice question
researchers conducted some experiment about metabolic reactions in a lab. they placed reactants into test tubes and tried measuring the activation energy and rate of the reactions in table 1. which of the statements about the reactions is true?
table 1: activation energy and metabolic rate in reactions
trail reactants activation energy metabolic rate
1 a + b 45.9 kj/mol not measured
2 a + b 25.9 kj/mol not measured
3 c + d not measured 8.9×10² l/mol
4 c + d not measured 7.1×10² l/mol

o enzymes were added to the test tubes in trials 1 and 2.
o enzymes were added to the test tubes in trials 3 and 4.
o enzymes were present in all of the trials.
o enzymes were present in the test tubes in trials 2 and 4.

Explanation:

Enzymes lower the activation - energy of a reaction. In Trials 1 and 2, the same reactants (A + B) are used, but the activation energy in Trial 2 (25.9 kJ/mol) is lower than in Trial 1 (45.9 kJ/mol). This indicates that an enzyme was likely added in Trial 2 to lower the activation energy. For Trials 3 and 4 with reactants C + D, the activation energy is not measured, and we cannot infer the presence of enzymes from the given metabolic rate data alone.

Answer:

Enzymes were added to the test tubes in Trials 1 and 2.