How does an increase in reactant concentration generally affect the rate of a chemical reaction?

• A. It increases the rate of reaction.
• B. It has no effect on the rate of reaction.
• C. It decreases the rate of reaction.
• D. It causes the reaction to stop completely.

Answer: (A)

Verified step by step guidance

1. Understand that the rate of a chemical reaction depends on how often reactant particles collide with enough energy to react, which is described by collision theory.
2. Recognize that increasing the concentration of reactants means there are more particles per unit volume, leading to a higher frequency of collisions between reactant molecules.
3. Recall that the rate law for many reactions can be expressed as \(\text{rate} = k [A]^m [B]^n\), where \([A]\) and \([B]\) are reactant concentrations, and \(m\) and \(n\) are their respective reaction orders.
4. Note that increasing the concentration of a reactant increases the value of \([A]\) or \([B]\) in the rate law, which generally increases the overall rate of reaction if the reaction order with respect to that reactant is positive.
5. Conclude that, in general, an increase in reactant concentration leads to an increase in the rate of reaction because more frequent and effective collisions occur.