10.1 Reaction rates and equilibrium

Question 1

The rate of a chemical reaction measures…

Answer 1

…how fast a reactant is being used up or how fast a product is being formed.

Question 2

What can the rate of a reaction be defined as

Answer 2

The change in concentration of a reactant or a product in a given time

Question 3

rate =

Answer 3

change in concentration / time

Question 4

What are the units of rate of reaction

Answer 4

mol dm^-3 s^-1

Question 5

The rate of a reaction is fastest at the _______ of the reaction as each reactant is at its _______ concentration.

Answer 5

Fastest

Highest

Question 6

The rate of a reaction ______ ______ as the reaction proceeds because the reactants are being ______ ______ and their concentration ______.

Answer 6

Slows Down
Used Up
Decreases

Question 7

Once one of the reactants has been completely used up, the concentrations ______ ______ and the rate of reaction is _______.

Answer 7

Stop Changing

Zero

Question 8

Factors that can change the rate of reaction

Answer 8

Concentration (or pressure when reactants are gases)
Temperature
Use of a catalyst
Surface area of solid reactants

Question 9

What does the collision theory state

Answer 9

That two reacting particles must collide for a reaction to occur.

Question 10

A collision will be effective if two conditions have been met:

Answer 10

The particles collide with the correct orientation

The particles have sufficient energy to overcome the activation energy barrier of the reaction

Question 11

How does increasing the concentration affect the rate of reaction

Answer 11

When concentration is increased, the rate of reaction generally increases. Increases the number of particles in the same volume, particles closer together and collide more frequently. Therefore more effective collisions in given time

Question 12

How does increasing the pressure of a gas affect the rate of reaction?

Answer 12

When a gas is compressed into smaller volume, pressure increases and rate of reaction increases. Concentration increases as same number of gas molecules occupy smaller volume. Gas molecules closer together and collide more frequently, therefore more effective collisions in same time

Question 13

How to monitor the progress of a chemical reaction

Answer 13

Monitor the removal (decrease in concentration) of a reactant
Following the formation (increase in concentration) of a product

Question 14

Methods that can be used to determine the rate of reaction where a gas is produced

Answer 14

Monitoring the volume of gas produced at regular time intervals using gas collection
Monitoring the loss of mass of reactants using a balance

Question 15

What is volume of gas produced and mass loss both proportional to

Answer 15

The change in concentration of a reactant or product

Question 16

Method - Monitoring the production of a gas using gas collection
Decomposition of hydrogen peroxide

2H2O2 –MnO2 catalyst–> 2H2O + O2

Answer 16

1. Hydrogen peroxide is added to the conical flask and the bung is replaced
2. Initial volume of gas in measuring cylinder is recorded
3. Manganese dioxide catalyst is then added to conical flask and bung is replaced. Stop clock is started
4. The volume of gas produced in the measuring cylinder is recorded at regular intervals until the reaction is complete
5. The reaction is complete when no more gas is produced
6. Plot graph of total volume of gas produced against time
7. To calculate initial rate, draw tangent at t=0

Question 17

Equation for the reaction of calcium carbonate and hydrochloric acid

Answer 17

CaCO3 + 2HCl –> CaCl2 + CO2 + H2O

Question 18

Monitoring the loss of mass of reactants using a balance

Answer 18

Carbonate and acid are added to conical flask on a balance
Mass of flask and contents is recorded initially and at regular time intervals.
Reaction is complete when no more gas is produced so no more mass is then lost.
Graph of mass lost against time is plotted