Question 1

Which of the following best explains why kindling (small pieces of wood) is used to start a fire more easily than a large log?

Accepted Answer

Kindling has a greater surface area relative to its volume, increasing the reaction rate.

Question 2

A gold ring is chosen for jewelry because it does not tarnish or corrode easily. Which factor affecting reaction rate is most responsible for this property?

Accepted Answer

Gold has a low chemical reactivity, so its oxidation rate is very slow.

Question 3

Sodium metal must be stored under oil to prevent rapid reaction with air. What property of sodium is responsible for this?

Accepted Answer

Sodium is highly reactive with oxygen, leading to a fast oxidation rate.

Question 4

A hospital warns against open flames near oxygen tanks. Why is this necessary?

Accepted Answer

Higher oxygen concentration increases the rate of combustion reactions, making fires more dangerous.

Question 5

Which of the following will NOT increase the rate of a reaction between a solid and a liquid?

Accepted Answer

Decreasing the concentration of the liquid reactant.

Question 6

Why does powdered sugar dissolve faster in water than sugar cubes?

Accepted Answer

Powdered sugar has a greater surface area, increasing the rate of dissolution.

Question 7

A reaction rate doubles for every 10°C increase in temperature. If a reaction is carried out at 30°C and then at 50°C, by what factor does the rate increase?

Accepted Answer

$$8$$

Question 8

Which of the following best describes the role of a catalyst in a chemical reaction?

Accepted Answer

A catalyst increases the reaction rate without being permanently changed.

Question 9

Why are enzymes effective as biological catalysts even in very small amounts?

Accepted Answer

Enzymes can catalyze many reactions without being used up.

Question 10

Which of the following is an example of a heterogeneous catalyst?

Accepted Answer

A metal catalyst in a catalytic converter speeding up gas-phase reactions.

Question 11

A catalytic converter in a car uses a metal catalyst to convert carbon monoxide to carbon dioxide. What is the main advantage of using a catalyst in this process?

Accepted Answer

It allows the reaction to proceed rapidly at lower temperatures, reducing energy consumption.

Question 12

Which of the following scenarios best illustrates the effect of temperature on reaction rate?

Accepted Answer

A glow stick glows longer when placed in the freezer.

Question 13

Which of the following statements about catalysts is FALSE?

Accepted Answer

Catalysts change the equilibrium position of a reaction.

Question 14

A researcher wants to slow down a reaction by a factor of 4. If the rate halves for every 10°C decrease, by how much should she decrease the temperature?

Accepted Answer

$$20\ ^\circ \mathrm{C}$$

Question 15

Which of the following is a real-world example of increasing reaction rate by increasing surface area?

Accepted Answer

Using powdered coal instead of coal chunks in a furnace.

Question 16

Why do flour mills ban smoking and open flames?

Accepted Answer

Flour dust has a large surface area, making combustion reactions extremely rapid and potentially explosive.

Question 17

Which of the following best describes why cold-blooded animals are less active at lower temperatures?

Accepted Answer

Their metabolic reaction rates decrease as temperature decreases.

Question 18

Which of the following is an example of a homogeneous catalyst?

Accepted Answer

An enzyme catalyzing a reaction in an aqueous solution.

Question 19

Which of the following changes would NOT increase the rate of a reaction between zinc metal and hydrochloric acid?

Accepted Answer

Decreasing the surface area of the zinc.

Question 20

Why is BHT (butylated hydroxytoluene) added to packaged foods?

Accepted Answer

It slows down oxidation reactions, preserving food freshness.

Lesson 6.2: Factors Affecting Reaction Rates in Chemical Kinetics

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