Multiple choiceQuestion 1 · Recall
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By the end, you can explain qualitatively why increasing concentration or gas pressure changes reaction rate.
Concentration tells us how much solute is packed into a given volume. Increasing concentration puts more reacting particles into the same space.
With more particles nearby, a particle meets another reactant more often. Collision frequency increases, so the number of effective collisions per second usually increases and the rate rises.
In a quiet corridor, two people may pass without meeting. In a crowded corridor, meetings happen more often.
The analogy has a limit: a chemical collision still needs enough energy and suitable orientation. Crowding raises the number of chances, not the success of every chance.
Worked example: Concentration change
Hydrochloric acid reacts with magnesium. Explain why using hydrochloric acid instead of hydrochloric acid usually gives a faster reaction, at the same temperature.