Physical Chemistry

Question 1

Rate of chemical reaction depends on :

Answer 1

1) frequency of collisions

2) particles have to collide w/enough energy for collision to be successful

Question 2

You can work out speed of reaction by recording:

Answer 2

1) amount of product formed
2) amount of reactant used up
* divide by time taken

Question 3

Activation energy

Answer 3

AE is the minimum energy a particle needs for a successful collision

Question 4

catalyst

Answer 4

Catalyst is a substance that speeds up a reaction without being used up or changed after reaction

Question 5

How does using a catalyst effect rate of reaction ?

Answer 5

Catalysts speed up reaction
Because they provide an alternative pathway of lower activation energy meaning less time spent for particles to react= faster reaction

Question 6

Explain why increasing the temperature increases rate of reaction?(2 reasons)

Answer 6

• increase in temp= more kinetic energy= particles collide more
• the particles have to collide w/ a minimum amount of energy( ACTIVATION ENERGY) and when u increase the temp more particles have energy more than or equal to the AE = more successful collisions

Question 7

What is bond breaking?

Answer 7

When energy absorbed = endothermic reaction ( 🔺H = +ve)

Question 8

What is bond making?

Answer 8

When energy released= exothermic reaction (🔺H= -ve)

Question 9

How does changing the concentration effect rate of reaction

Answer 9

By increasing the concentration of acid, we increase the NUMBER OF ACID PARTICLES in a fixed volume—
particles are closer together + COLLIDE MORE FREQUENTLY= more SUCCESSFUL COLLISIONS

Question 10

Rate of reaction

Answer 10

How fast reactants are turned into products

Question 11

What word is used to describe a reaction in which there is a temperature rise

Answer 11

Exothermic

Question 12

What word is used to describe a reaction where the temperature has dropped

Answer 12

Endothermic

Question 13

Endothermic

Answer 13

Reactions in which heat energy is taken in from the surroundings 🥶

Question 14

Exothermic

Answer 14

Reactions in which heat energy is given out to the surroundings 🔥

Question 15

In exothermic reactions what has more chemical energy: the products or the reactants?

Answer 15

The reactants have more chemical energy
The products have less chemical energy

Chemical energy—> heat energy

(Heat energy released to surroundings)

Question 16

In endothermic reactions what has more chemical energy: the products or the reactants?

Answer 16

The products have more chemical energy
The reactants have less chemical energy

Heat energy—> chemical energy

Question 17

What is enthalpy change a measure of ?

Answer 17

The amount of heat energy taken in or given out in a chemical reaction.

Has the symbol: 🔺H

Question 18

Green Copper(ii)carbonate thermally decomposes to what (give colours change) and what type of reaction is this ?

Answer 18

It’s an endothermic reaction

Upon thermal decomposition it produces copper (ii) oxide which is BLACK

Question 19

Define the specific heat capacity of a substance

Answer 19

Amount of heat needed to raise the temperature of 1 gram of a substance by 1^C

Question 20

How does one work out the MOLAR ENTHALPY CHANGE after obtaining (Q= heat energy change)

Answer 20

1) work out number of MOLES of the substance burned/reacted
moles= mass/RAM

2) now work out enthalpy change: by plugging in the Q value (heat energy change)
molar enthalpy change= Q/ number of moles of the substance

Question 21

Set up a dissolving experiment to measure enthalpy change using calorimetry

Answer 21

~ set up a polystyrene cup insulated with cotton wool containing the reaction mixture and a thermometer

Put water in cup + record temp
Then add anhydrous copper (ii) sulfate
Stir + record temp

Question 22

Set up a neutralisation experiment to measure enthalpy change using calorimetry

Answer 22

~ set up a polystyrene cup insulated with cotton wool containing the reaction mixture and a thermometer

Put dry citric acid + dry sodium hydrogen carbonate to the cup + record temp
Then separately get some water and measure the temp (of it alone)
Now add the water to the dry mix + record temp

Question 23

Set up a displacement experiment to measure enthalpy change using calorimetry

Answer 23

~ set up a polystyrene cup insulated with cotton wool containing the reaction mixture and a thermometer

Put copper(ii) sulfate solution in cup + record temp
Then add powdered zinc
Stir + record temp

Question 24

What is the effect of increasing pressure on rate of reaction of gases

Answer 24

Increasing pressure of gases, increases the rate of reaction because the particles r much closer together, which means they collide more frequently= MORE SUCCESSFUL COLLISIONS

Question 25

What state does increasing pressure have no effect on and why

Answer 25

Particles in Liquids + solids r very close together and r affected v little by changes in pressure

Question 26

What happens to the rate of reaction of marble chips in hydrochloric acid if you increase the surface area of the marble chips

Answer 26

The rate of reaction will increase when the SA increases (smaller chip)
Cos there r more surfaces in contact w the acid, So the frequency of successful collisions increases

Question 27

Do catalysts change by the end of a reaction ?

Answer 27

NO! Catalysts are left unchanged and are not used up in a reaction

Question 28

Design an experiment to investigate the rate of reaction of calcium carbonate reacting with HCl acid

Answer 28

Put calcium carbonate with HCl acid in a conical flask with a rubber stopper to stop CO2 gas escaping

Attach a gas syringe to the conical flask + measure the CO2 produced

Measure the time taken for the reaction to take place (no more bubbling)

Use amount of product formed
—————————————
Time taken

= rate of reaction

Question 29

Why are catalysts important in industry

Answer 29

Catalysts r important in industry cos they make substances react quickly at lower temperatures + pressures which would otherwise be necessary
THIS SAVES MONEY 💸💸💸💸💸💸

Question 30

Is bond breaking an exothermic or endothermic process

Answer 30

Bond breaking = endothermic process

Question 31

Is bond making an exothermic or endothermic process

Answer 31

Bond making = exothermic process

Question 32

Set up a calorimetry experiment of COMBUSTION to calculate enthalpy change

Answer 32

1) set up a copper can w water and a thermometer, now underneath the can fill a spirit burner with alcohol
2) record the temperature of the water b4 + weigh the spirit burner and lid
3) light the wick and wait till it reaches 50*C— put out flame
4) weigh spirit burner + lid AGAIN
5) calculate enthalpy change

USE A DRAUGHT EXCLUDER = to prevent unwanted heat loss to surroundings

Question 33

Energy change =

Answer 33

Energy change = sum of BONDS BROKEN - sum of BONDS MADE

Question 34

If more energy is released during bond making .. what kind of reaction is it?

Answer 34

More energy is released during bond making so it is an exothermic reaction

-🔺H = exothermic

Question 35

If more energy is released during bond breaking.. what kind of reaction is it?

Answer 35

More energy is released during bond breaking so it is an endothermic reaction

+🔺H = endothermic

Question 36

What is the effect of temperature on yield

Answer 36

Increasing the temperature increases the rate of reaction BUT DECREASES THE YIELD