Energetics

Question 1

Exothermic reaction

Answer 1

When energy is given out (usually as heat energy) but it can be given out as light, sound or even electrical energy aswell

Question 2

What are exothermic process

Answer 2

Condensing and freezing

Question 3

Process of the exothermic reaction

Answer 3

When a gas condenses to a liquid or a liquid freezes to a solid, energy is given our as new bonds between the particles form

Question 4

Reactants

Answer 4

What’s going in

Question 5

Products

Answer 5

What’s going out

Question 6

Endothermic reaction

Answer 6

A reaction is described as endothermic when energy is taken in from the surroundings. It is observed by a drop in temperature of the surroundings

Question 7

Endothermic process

Answer 7

When a solid melts to a liquid or a liquid boils to a gas, energy is taken into break the bonds between the particles

Question 8

Endothermic processes

Answer 8

Melting and boiling

Question 9

Why do reactions give out or absorb energy?

Answer 9

To break a chemical bind energy must be put intro the bond- endothermic

When a new chemical bond forms energy is released- exothermic

Question 10

Mexobendo

Answer 10

Making- exothermic

Breaking- endothermic

Question 11

Delta H Of the reaction=

Answer 11

E bond breaking - E bond making

Question 12

If E bond breaking is less than E bond making then

Answer 12

• DELTA H

Exothermic

Question 13

If E bond breaking is bigger than E bond making then

Answer 13

+ Delta H

ENDOTHERMIC

Question 14

What does the bond energy measure?

Answer 14

The average amount of energy (in KJ/mol) needed to break a particular bond in the gas phase

Question 15

Bond energies can be used to….

Answer 15

Estimate the enthalpy of a reaction

Question 16

Q=

Answer 16

McdeltaT

Question 17

Q

Answer 17

Heat energy (joules, J)

Question 18

m

Answer 18

Mass of water

Question 19

Specific heat

Answer 19

4.18 Jg-1 or oC-1

Question 20

Delta T

Answer 20

Temperature change

Question 21

To convert J to KJ

Answer 21

Divide by 1000

Question 22

Delta H

Answer 22

= Q/n

Question 23

n

Answer 23

Number of moles

Question 24

Delta H

Answer 24

Enthalpy change (KJ mol-1)

Question 25

N=

Answer 25

Moles= mass/rfm

Question 26

Make sure volume=

Answer 26

Dm3

Question 27

Moles = mass/rfm or

Answer 27

Concentration x RFM

Question 28

In the the exothermic reaction, why does it take in heat?

Answer 28

Because breaking bond takes in energy, and making bonds gives out energy former exceeds the later

Question 29

Why is the match needed to start the reaction, but once it continues without further heating

Answer 29

Match supplies the activation energy the reaction supplies it after that

Question 30

Comparing the heat energy produced by combustion of various alchohols

Answer 30

1) fill conical flask with 100cm3 of water. 2) weigh the spirit burner and lid containing the alchohol and record the mass and name of the alchohol 3) record the initial temperature of the water using the thermometer. 4) place the spirit burner under the vincula flask and light the wick. 5) allow the alchohol to heat the water so the temperature rises by about 40oc 6) replace the cap after blowing out the flame 7) rewrite the spirit burner and cap and work out the mass of alcahol used Repeat for different alcahol use 100cm3 of new water each time

Question 31

Neutralisation caloritimatry experiment

Answer 31

1) measure out copper sulphate solution into a well insulated container and then measure its temperature. Add zinc powder. Stir gently and continuously and note the highest temperature reached. Work out the temperature change. Then repeat part 1 using Citrix acid and sodium hydrogencarbonste, record the temp change as before

Question 32

Methanol

Answer 32

CH3OH

Question 33

Ethanol

Answer 33

C2H6O

Question 34

Propanol

Answer 34

C3H8O

Question 35

Example of an exothermic reaction

Answer 35

The thermit reaction

Question 36

Delta H

Answer 36

Temp change

Question 37

Example of an exothermic reaction

Answer 37

The thermit reaction

Question 38

Delta H

Answer 38

Temp change