Reaction Rates

Question 1

what is the rate of a reaction

Answer 1

how quickly a reaction happens

Question 2

what are the two ways that the rate of reaction can be measured

Answer 2

• by measuring how quickly the reactants are used up

- or measuring how quickly the product is formed

Question 3

what is the formula for calculating the rate of reaction

Answer 3

rate of reaction = how much of the reactants are used up or how much product if formed / time

Question 4

what are the 3 experimental measurements used to measure rate of reaction

Answer 4

• precipitation
• change in mass
• volume of gas given off

Question 5

what type of reactions would the method of precipitation work in

Answer 5

• any reaction where mixing two see-through solutions produces a precipitate
• which clouds the solution

Question 6

how is the method of precipitation carried out

Answer 6

how is the method of precipitation carried out

Question 7

what is the rate at which the mixture obscures the mark in the precipitation method measuring

Answer 7

• the rate of reaction between the two solutions

- when they react, a precipitate is formed which clouds the solution

Question 8

if the mark on the paper quickly disappears in the precipitation method, what does it indicate

Answer 8

a quick reaction, so the rate of reaction is high

Question 9

what is a disadvantage of the precipitation method

Answer 9

• the result is subjective

- different people might not agree on exactly when the mark disappears

Question 10

what is a mass balance used for

Answer 10

measuring the rate of a reaction that produces a gas

Question 11

while measuring the change in mass, how does a mass balance indicate the rate of a reaction

Answer 11

• during reaction, as gas is released
• lost mass is easily measured on the balance
• the quicker the reading on the balance drops, the faster the reaction

Question 12

ho do you know when a reaction has finished in the change in mass method and why

Answer 12

• when the reading on the balance stops changing
• because no more mass is being lost
• so no more gas is being released
• meaning the reaction has stopped

Question 13

how can your results in the change in mass method be visually displayed

Answer 13

by plotting a graph of change in mass against time

Question 14

what is a disadvantage of the change in mass method

Answer 14

• method releases gas produced into the room

- if gas is harmful, safety precautions must be taken

Question 15

why would you put cotton wool in the mouth of a flask during the change in mass method

Answer 15

• the cotton wool let’s gases through

- but stops any solid, liquid or aqueous reactants flying out during the reaction

Question 16

how is the volume of gas given off in the ‘volume of gas given off’ method measured with

Answer 16

a gas syringe

Question 17

how is a faster reaction indicated in the volume of gas given off method

Answer 17

• more gas is given off during a set time interval

- shown by the gas syringe filling up at a quicker rate

Question 18

how can you tell when the reaction has finished in the volume of gas given off method

Answer 18

when no more gas is produced and the gas syringe reading doesnt change

Question 19

how would you plot your results on a graph from the volume of gas given off method

Answer 19

you would plot the graph of gas volume against time elapsed

Question 20

what is a disadvantage of the volume of gas given off method

Answer 20

• need to be careful using youre the right size gas syringe

- if reaction is too vigorous, the plunger can be blown off the end of the syringe