Humber Admissions Practice Test

Which factors influence reaction rates?

1. Nature of reactants only

2. Concentration and temperature only

3. Surface area and catalysts only

4. Nature of reactants, concentration, surface area, presence of catalysts, and temperature

The correct answer is: Nature of reactants, concentration, surface area, presence of catalysts, and temperature

The correct choice encompasses a comprehensive range of elements that significantly affect reaction rates. Understanding these factors is paramount in chemistry, as each plays a crucial role in how fast or slow a reaction proceeds. The nature of reactants refers to the specific characteristics of the substances involved in the reaction, including their physical state (solid, liquid, gas), bond strengths, and chemical properties. These attributes determine how effectively reactants can collide and interact, impacting the speed of the reaction. Concentration indicates the amount of a substance present in a given volume. Higher concentrations typically lead to more frequent collisions between reactant particles, thereby increasing the likelihood of reaction and reducing the time taken for the reaction to occur. Surface area is particularly relevant for solid reactants. Finely divided solids provide more area for reactions to take place, increasing contact between reactants and enhancing the reaction rate. This is why powdered substances often react faster than larger chunks. The presence of catalysts can dramatically alter reaction rates. Catalysts provide an alternative pathway for the reaction with a lower activation energy, enabling the reaction to occur more quickly without being consumed in the process. Temperature also plays a critical role. Increasing temperature generally results in higher kinetic energy for the reactants, leading to more collisions and a greater likelihood