Question

Why couldn't you substitute 3m H2SO4 for concentrated HNO3 when oxidizing copper?

Answer 1

Every oxidizing agent has different properties and they are specific for different reagents. Different solution of oxidizing agent will have different strength.

Sulfuric acid or H2SO4 is weaker oxidizing agent when compared to nitric acid (HNO3). so when you use H2SO4 for the oxidizing copper it would not work because copper need strong oxidizing agent.

Answer 2

This question seems to be an essay question from experiment. Different solution of oxidizing agent will have different strength. Sulfuric acid or H2SO4 is weaker oxidizing agent when compared to nitric acid (HNO3). In this case, if you subtitute the H2SO4 you wouldn't be able to get the same result for the experiment.