help? Week 1: PART 2: Factors that affect the rate of chemical reactions. In Tab

ID: 1027938 • Letter: H

Question

help?

Week 1: PART 2: Factors that affect the rate of chemical reactions. In Table 1, qualitatively discuss how reaction rate changes with respect to each variable (e.g., concentration, temperature, nature of the reactants (solid versus liquid), and stirring Table 1: Effect of concentration, temperature, nature of reactants and stirring on the reaction rate. Variable Effect on reaction kinetics Concentration Temperature Nature of the reactants (solid versus liquid) Mixing PART 3: Using concentration to determine the rate order

Explanation / Answer

Variable

Effect on reaction kinetics

Concentration

The rate of a reaction may or may not depend on the concentration of the reactants. For zero order reactions, the rate is independent of the concentration of the reactants. Hence, changing the concentration of the reactants will have no effect on the rate of a zero order reaction.

Poly order (first, second, etc) reactions depend on the concentration of the reactants. Increasing the concentrations of the reactants increases the rate of the reaction while decreasing the concentrations reduces the rate. For example, doubling the concentration of a reactant doubles the rate of a first order reaction while a second order reaction has its rate increased by four times.

Temperature

The rate of a reaction increases with increase in temperature while a decrease in temperature reduces the rate.

Nature of the reactants (solid versus liquid)

As with concentration, first and second order reactions depend on the nature of the reactants. A solid reactant will react more slowly since the bonds in a solid are stronger than those in a liquid. A chemical reaction involves breaking of bonds in the reactants and formation of new bonds in products. Since the bonds in a solid are stronger, hence, more energy is required to break the bonds and consequently, the reaction proceeds slowly.

A liquid reactant has lower bond energy and hence, the bond breaking and bond making can proceed faster, thereby, increasing the rate of the reaction.

Mixing

Mixing the reactants usually by stirring with a rod, etc, increases the reaction rate. This is due to the fact that mixing increases the probability of the reactant molecules colliding with each other and successful collisions lead to reaction products.