Rate of Reaction Concepts

Question 1

What is a physical change?

Answer 1

A physical change is an alteration of a substance that is irreversible an example of this is toasting bread, once the bread becomes toast it is no longer possible to revert the toast into bread again.

Question 2

What is a chemical change?

Answer 2

An Irreversible rearrangement of atoms of one or more substances and a change in their chemical properties resulting in the formation of one or more new substances.

Question 3

What is a chemical Reaction

Answer 3

A reaction in which reactants react with each other to create products

Question 4

What is a combustion Reaction

Answer 4

Fuel + Oxygen gas -> Carbon Dioxide + Water Vapour

Question 5

What is the outcome of an Acid + base reaction?

Answer 5

Salt + Water

Question 6

What is the outcome of an Acid + Metal reaction

Answer 6

Salt + Hydrogen Gas

Question 7

What is the outcome of a Water + Metal reaction

Answer 7

metal hydroxide + hydrogen gas

Question 8

Acid + carbonate/hydrogen carbonate

Answer 8

Salt + carbon dioxide + water

Question 9

How can the rate of reaction be measured?

Answer 9

Amount of products produced over a certain amount of time

Question 10

Endothermic reaction

Answer 10

An endothermic reaction is any chemical reaction that absorbs heat from its environment to form products.)

Question 11

Exothermic reaction

Answer 11

An exothermic reaction is a reaction in which energy is released through light or heat.)

Question 12

Characteristics of Endothermic reactions

Answer 12

Takes more energy for bonds to be broken than the amount of energy released to create new ones. Energy is absorbed. Enthalpy is positive

Question 13

Characteristics of Exothermic reactions

Answer 13

Takes less energy for bonds to be broken than the amount of energy released to form new ones. Energy is released. Enthalpy is negative

Question 14

Activation Complex

Answer 14

The intermediate phase is where reactant particles are breaking however product bonds have not formed yet

Question 15

Explain the impact that temperature has on the rate of reactions using collision theory

Answer 15

At higher temperatures collisions are more energetic and more likely to have a sufficient amount of energy for a reaction to occur.

Question 16

Explain the impact that concentration has on the rate of reactions using collision theory

Answer 16

The higher the concentration the more chance there is of collisions between reactant particles this is because there are more molecules per unit of volume and more collisions result in more reactions.

Question 17

Explain the impact that surface area has on the rate of reactions using collision theory

Answer 17

The larger the surface area, the more increased collisions between reactants, thus a higher rate of reaction

Question 18

Explain the impact that catalysts has on the rate of reactions using collision theory

Answer 18

This speeds up the rate of reaction by lowering the activation energy since it speeds up reactants more collisions are likely to occur that result in reactions

Question 19

Catalysts

Answer 19

A substance that speeds up the reaction rate by decreasing the required activation energy

Question 20

Catalytic Converter

Answer 20

An exhaust emission control device that converts toxic pollutant gases produced the by engine into less toxic pollutants

Question 21

Functions of an Enzyme

Answer 21

Enzymes are biological catalysts that increase the rate of biological reactions. Each enzyme is a distinct 3D shape which allows it to perform one specific chemical reaction.

Question 22

Optimum conditions for enzyme activity

Answer 22

The optimum conditions for enzyme activity are approximately 37oC and a PH level between 6-8

Question 23

The effect of an increase in concentration on enzyme activity

Answer 23

An increase in enzyme concentration can speed up the rate of reaction however this is because there are more enzymes to bind the substrates to form products in a reaction. Once all enzyme molecules are bound to a substrate an increase in concentration for either will not alter the rate of reaction

Question 24

Competitive Inhibitor

Answer 24

When an inhibitor is bound to an enzyme’s activity site, in turn blocking the substrate from binding. The inhibitor then competes with the substrate for the enzyme

Question 25

Non Competitive Inhibitor

Answer 25

When an inhibitor binds to a site other than the active site (also known as the allosteric site) of an enzyme it causes a change in shape to the active site. This then causes the enzyme to not be able to bind to the active site.

Question 26

Reversible Reactions

Answer 26

A reversible reaction is a reaction in which the products and reactants are engaged in a forward and backward reaction occurring at the same time.)

Question 27

Dynamic Equilibrium

Answer 27

When the forwards and backward reactions take place at the same time, this does not mean that the reaction has stopped just that both reactions continue at an equal rate

Question 28

Le Chatelier’s Principle

Answer 28

This principle states that if a change is applied to a system in equilibrium, the system changes to counteract that stress or change.

Question 29

Effect of temperature in change in equilibrium

Answer 29

If the temperature is lowered in a system in equilibrium the system adjusts itself to counteract the change by producing more heat

Question 30

Effect of pressure in change in equilibrium

Answer 30

Pressure can only affect equilibrium systems in which some substances are present during the gas phase, the pressure will only affect systems in which there are a different number of molecules of gases on the reactant and product sides of the equation.

Question 31

Effect of concentration in change in equilibrium

Answer 31

If more of one reactant is applied to a system in equilibrium, the system changes it position by adding and producing more products to reach a new equilibrium

Question 32

The Haber Process explained with Le Chatelier’s principle

Answer 32

At room temperature and at standard pressure no ammonia was produced, so to favour the forward reaction (side that produces ammonia). Decreasing the temperature will end up producing more ammonia at equilibrium, however, it may take months to produce ammonia at low temperatures so having the temperature at 450oC is a compromise as despite less ammonia being gained at equilibrium it’s gained much quicker. Increasing the pressure promotes a volume of gases and in this case, moving the reaction to the right and an iron catalyst is used to speed up the process of getting the reaction to reach equilibrium