Question

(a) Select all of the correct statements about reaction rates from the choices below.

1.The lower the rate of a reaction the longer it takes to reach completion.

2.The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step.

3.Slow reactions can be speeded up by raising the temperature.

4.Solid catalysts increase reaction rates as their surface areas increase.

5.The rate of a fast step has more effect on the overall reaction rate than the rate of a slow step.

6.The fastest step in a reaction is called the rate-determining step.

7.Reactions involving very unstable combinations of chemicals have small rate constants.

Answer 1

Let us consider each statement.

1.The lower the rate of a reaction the longer it takes to reach completion: TRUE

Consider the instantaneous rate of a reaction, where the reactant A is converted into product B.

As we can see, rate is inversely proportional ti time. Slower the rate greater the time taken for completion.

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2.The rate of a slow step has more effect on the overall reaction rate than the rate of a fast step:TRUE

5.The rate of a fast step has more effect on the overall reaction rate than the rate of a slow step:FALSE

6.The fastest step in a reaction is called the rate-determining step:FALSE

The slowest step of the reaction is called the rate determining step. If the 1st step of a reaction is the slowest, we can assume that the overall rate of the reaction is equal to the rate of that step.

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3.Slow reactions can be speeded up by raising the temperature:TRUE

For molecules to react, they should collide in proper orientation and energy. Increasing the temperature increases the collisions between molecules and also increases the proportion of molecules in the system with energy greater than ot equal to the activation energy.

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4.Solid catalysts increase reaction rates as their surface areas increase:TRUE

Consider the catalytic conversion of hydrogen peroxide into water. Manganese dioxide catalysts is used here and oxygen is produced faster if manganese dioxide is in the form of powder, rather than granules.

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7.Reactions involving very unstable combinations of chemicals have small rate constants:FALSE

Unstable reactants have high rates, and inturn large rate constants.