Energetics/rates/equilibria

Question 1

What do the rates of reactions depend on?

Answer 1

Temperature
Concentration
Catalyst
Size of particles

Question 2

Rate of reaction equation

Answer 2

Amount of reactant used/amount of product formed divided by time

Question 3

What can be used to measure the volume of gas

Answer 3

Gas syringe

Question 4

Advantage of using a gas syringe

Answer 4

Gives volumes accurate to the nearest mm

Question 5

Disadvantage of using a gas syringe

Answer 5

If the reaction is too vigorous, you can easily blow the plunger out the end of the syringe

Question 6

Why put cotton wool at the top of the conical flask in the reaction of hydrochloric acid and marble chips

Answer 6

Stops acid spray leaving the flask (but let’s CO2 escape)

Question 7

What does a gas need to be to use an inverted measuring cylinder

Answer 7

Insoluble or sparingly soluble in water

Works for: oxygen, hydrogen and carbon dioxide

Question 8

What does the rate of reaction depend on (collision wise)

Answer 8

How many successful high energy collisions there are in a given unit of time

Question 9

Affect of size of particles on rate of reaction

Answer 9

Large particles, smaller surface area, fewer collisions, slower reaction

Smaller particles, larger surface area, more collisions, faster reaction

Question 10

How can you test the affect of surface area on something

Answer 10

Do the experiment once with marble chops and another time with marble power
Use 5g of marble and 100cm3 of dilute Hcl in each

Question 11

Why is the experiment faster with marble powder

Answer 11

5g of marble used in both cases so the graph levels off at the same point

The reaction is faster for the powder because there are more frequent collisions due to the greater surface area of the powder

Question 12

Effect of Concentration on rate of reaction

Answer 12

Low concentration of solution, fewer acid particles in solution, therefore fewer collisions in the same time and slower rate

High concentration of solution, more acid particles in the same volume of solution, therefore more frequent collisions and faster rate

Question 13

Effect of increasing temp on rate of reactions

Answer 13

Increasing temp increases the kinetic energy of the particles, the frequency of collisions increases and the proportion of high energy collisions increases

Question 14

Improvement for temp experiments

Answer 14

Use a thermostatically controlled water bath to keep the temp constant

Question 15

Exothermic reaction

Answer 15

Heat energy given out (small activation energy)

Question 16

Endothermic reaction

Answer 16

Heat energy taken in (large activation energy)

Question 17

What does an increase of pressure do to the rate of reactions

Answer 17

Increases the rate of reactions between gases but hardly affects the rate of reactions between liquids, solutions and solids (molecules/atoms/ions are already very close together)

Question 18

What is a catalyst

Answer 18

Substance that speeds up a chemical reaction but is in unchanged in mass and is unchanged chemically during the reaction.

Question 19

What does a catalyst do

Answer 19

Speeds up the reaction by providing an alternative reaction pathway of lower activation energy

Question 20

What do catalytic converters do

Answer 20

Change the pollutant exhaust gases carbon monoxide and nitrogen dioxide into harmless carbon dioxide and nitrogen

Question 21

What does process of making chemical bonds do

Answer 21

Give out energy (temp increases = exothermic)

Question 22

What does process of breaking chemical bonds do

Answer 22

Requires energy (temp decreases = endothermic)

Question 23

DeltaH negative

Answer 23

Exothermic

Question 24

DeltaH positive

Answer 24

Endothermic

Question 25

Reactions that result in an energy change

Answer 25

Combustion (always exo)
Dissolving (either)
Neutralisation (always exo)
Displacement

Question 26

Sources for error in burning liquids:

Answer 26

Heat lost to the surroundings

Heat used to raise the temp of the flask and the thermometer

Question 27

How to reduce sources of error in burning liquids

Answer 27

Put screen around apparatus to reduce draft

Question 28

Metal + acid >

Answer 28

Salt + hydrogen

Question 29

Heat given out =

Answer 29

Mass x 4.2 (specific heat capacity) x temp rise

Question 30

Reversible reaction

Answer 30

When the products can react to form reactants

Question 31

Hydrogen + nitrogen > ammonia

Answer 31

Forward reaction

Question 32

Ammonia > hydrogen + nitrogen

Answer 32

Backward reaction

Question 33

Dynamic

Answer 33

Both the forward and backward reaction are happening at the same rate

Question 34

Equilibrium

Answer 34

Reaction has reached a point where the overall amounts of reactants and products do not change

Question 35

Dynamic equilibrium

Answer 35

Concentration of reactants and products remain constant

Question 36

When is the equilibrium on the left hand side

Answer 36

When there are large amounts of reactants remaining and small amounts of products present

Question 37

When the equilibrium is on the right hand side

Answer 37

Large amounts of products have formed and very little of the reactants remain

Question 38

How are reactants and products in an equilibrium affected by pressure

Answer 38

Increasing pressure moves the equilibrium in the direction of fewer moles of gas

Decreasing pressure moves the equilibrium in the direction of more moles of gas

Question 39

How are reactants and products in an equilibrium affected by temp

Answer 39

Increasing temp moves the equilibrium in the endothermic direction

Decreasing temp moves the equilibrium in the endothermic direction

Question 40

+ ive

Answer 40

Endothermic

Question 41

• ive

Answer 41

Exothermic

Question 42

Effect of catalyst on position of equilibrium and rate of reaction

Answer 42

Speeds up forward and reverse reactions equally so has no effect on the position of the equilibrium