Question

1. in chemical reactions, electricity, a spark, and sunlight are all ways in which ____________ may be provided.

(a) reactants
(b) products
(c) activation energy
(d) catalysts

1. which of the following will slow down the rate of a chemical reaction?

(a) increasing the surface area of the reactants
(b) increasing the concentration of reactants
(c) addition of a catalyst
(d) decreasing the temperature
(e) increasing the pressure

1. for an effective collision to take place, there must be (choose two answers)

(a) a sufficiently hard collision
(b) a catalyst present
(c) a correctly oriented collision
(d) high pressure
(e) no products present

Explanation:

1. Activation energy can be provided in forms like electricity, a spark, and sunlight in chemical reactions. Reactants are the starting - materials, products are the end - results, and catalysts speed up reactions without being consumed.
2. Increasing surface area, concentration, adding a catalyst, and increasing pressure generally speed up reactions. Decreasing temperature slows down the motion of reactant particles, thus slowing down the reaction rate.
3. For an effective collision (which leads to a reaction), there must be sufficient energy (sufficiently hard collision) and correct orientation of the colliding particles. A catalyst can increase the frequency of effective collisions but is not a requirement for an effective collision to occur initially, high pressure is not a necessary condition for every effective collision, and the absence of products is not a condition for an effective collision.

Answer:

1. C. activation energy
2. D. Decreasing the temperature
3. A. A sufficiently hard collision, C. A correctly oriented collision