Yield and Rates of reaction

Question 1

Percentage Yield

Answer 1

Amount of substance made ÷ theoretical amount X 100

Question 2

Explain why reactions are never have a 100% yield.

Answer 2

because it is reversible reaction.

Some of the product may be lost when it is separated from the reaction mixture.

Some of the reactants may react in ways different from the expected reaction

Question 3

Reversible reactions

Answer 3

Means the products of the reaction can react to produce the original reactant.

Question 4

Rate of reaction

Answer 4

Is the speed of a reaction

Can be calculated by dividing amount of reactant use by time

Or

By dividing amount of product made by time.

Question 5

Activation energy

Answer 5

The minimum amount of energy particles must have to react.

Question 6

Successful collision

Answer 6

When a particle collides in the correct direction with the minimum energy (activation energy) – this is when a chemical reaction happens.

Not all collisions are successful

Question 7

Explain how increasing temperature affects the Rate of Reaction.

Answer 7

Increases the speed/kinetic energy of the reacting particles

so that they collide more frequently

and more energetically.

This increases the rate of reaction.

Question 8

Explain how increasing concentration affects the Rate of Reaction.

Answer 8

Increases the frequency of collisions

as there are more particles per cm3 of solution

and so increases the rate of reaction.

Question 9

Explain how increasing pressure affects the Rate of Reaction.

Answer 9

Increases the frequency of collisions

more particles per cm3 of solution

and so increases the rate of reaction.

Question 10

Explain how increasing surface area affects the Rate of Reaction.

Answer 10

Increases the frequency of collisions

as there are more particles exposed to react

Question 11

Explain how catalyst affects the Rate of Reaction.

Answer 11

Change the rate of reaction

as catalyst provide a different pathway with a lower activation energy

so more molecules with have the lower activation energy

so increases the rate of reaction.

they are not used up

Question 12

Exothermic Reaction

Answer 12

is one that transfers energy from the chemical bond to the surroundings – gets hotter

Question 13

Endothermic Reaction

Answer 13

is one that takes in energy from the surroundings – gets colder