SCH4U Reaction Rates

Which of the following statements about "a reaction rate" is INCORRECT?

• the rate of a reaction describes how fast a reaction proceeds over volume of time

• a rate of reaction measures how quickly reactants are changed into products.

• is the change in concentration of reactants over time or the change in concentration of products over time

• Units for reaction rates are in terms of M (mols/L) /time.

• None of the other 4 statements are INCORRECT.

T/F - When expressing reactions rates that following rule is applied. For faster reactions, seconds are used for units of time; for longer reactions, minutes are used.

• True

• False

Which of the following statements about "a reaction rate" is INCORRECT?

• the rate of a reaction describes how fast a reaction proceeds over time.

• reaction rates may be expressed in terms of any chemical species involved in the reaction.

• reaction rate can be written for the disappearance of a reactant or the appearance of a product.

• Units for reaction rates are in terms of M (mols/L) /time.

• None of the other 4 statements are INCORRECT.

When combined hydrochloric acid and zinc metal the acid eats away at the metal to produce hydrogen gas and some dissolved metal salts. The rate of this reaction could be measured in terms of the disappearance of the zinc or the rate of appearance of hydrogen gas.

If we were expressing reaction rate in terms of disappearance of zinc metal, we would write:

• Reaction rate = - change[zinc]/time

• Reaction rate = change[zinc]/time

When combined hydrochloric acid and zinc metal the acid eats away at the metal to produce hydrogen gas and some dissolved metal salts. The rate of this reaction could be measured in terms of the disappearance of the zinc or the rate of appearance of hydrogen gas.

If we were expressing reaction rate in terms of disappearance of zinc metal, we could conclude that following

• The slope of the line would be negative, because the concentration of our reactant is constantly decreasing.

• The slope of the line would be positive, because the concentration of our reactant is constantly decreasing.

• The slope of the line would be negative, because the concentration of our reactant is constantly increasing.

T /F - The random bumping and colliding of molecules with each other generally do not contain enough energy to break these bonds and cause a chemical reaction.

• True

• False

According to collision theory, in order for a chemical reaction to happen there needs to be an effective collision between the reactants. To be effective, a collision must meet the following two requirements:

• Molecules collide with enough energy to break bonds

• Molecules collide with a favorable orientation

Which of the following statements about "the factors that can affect a reaction rate" is INCORRECT.

• Increasing concentration decreases the number of effective collisions.

• Increasing temperature increases the kinetic energy of the particles, leading to more effective collisions.

• Increasing surface area increases the particles available to react, increasing the likelihood of effective collisions.

• Addition of a catalyst increases reaction rate by decreasing the amount of energy needed for a reaction to occur.

• None of the other 4 statements are INCORRECT.

Which of the following statements about "temperature and it's relationship to rates of reaction" is INCORRET?

• Temperature is a measurement of the energy in motion within a system.

• The higher the temperature, the more energy the system has.

• Molecules with more energy are likely to have more effective collisions with each other, resulting in an increased rate of reaction

• None of the other 3 statements are INCORRECT.

T/F - A catalyst is a substance that increases the rate of reaction but does not participate in the reaction itself. The catalyst remains unchanged.

• True

• False