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Chemsitry > Energetics > Flashcards

Energetics Flashcards

1
Q

Exothermic reaction

A

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

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2
Q

What are exothermic process

A

Condensing and freezing

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3
Q

Process of the exothermic reaction

A

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

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4
Q

Reactants

A

What’s going in

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5
Q

Products

A

What’s going out

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6
Q

Endothermic reaction

A

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

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7
Q

Endothermic process

A

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

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8
Q

Endothermic processes

A

Melting and boiling

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9
Q

Why do reactions give out or absorb energy?

A

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

When a new chemical bond forms energy is released- exothermic

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10
Q

Mexobendo

A

Making- exothermic

Breaking- endothermic

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11
Q

Delta H Of the reaction=

A

E bond breaking - E bond making

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12
Q

If E bond breaking is less than E bond making then

A
  • DELTA H

Exothermic

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13
Q

If E bond breaking is bigger than E bond making then

A

+ Delta H

ENDOTHERMIC

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14
Q

What does the bond energy measure?

A

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

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15
Q

Bond energies can be used to….

A

Estimate the enthalpy of a reaction

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16
Q

Q=

A

McdeltaT

17
Q

Q

A

Heat energy (joules, J)

18
Q

m

A

Mass of water

19
Q

Specific heat

A

4.18 Jg-1 or oC-1

20
Q

Delta T

A

Temperature change

21
Q

To convert J to KJ

A

Divide by 1000

22
Q

Delta H

A

= Q/n

23
Q

n

A

Number of moles

24
Q

Delta H

A

Enthalpy change (KJ mol-1)

25
Q

N=

A

Moles= mass/rfm

26
Q

Make sure volume=

A

Dm3

27
Q

Moles = mass/rfm or

A

Concentration x RFM

28
Q

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

A

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

29
Q

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

A

Match supplies the activation energy the reaction supplies it after that

30
Q

Comparing the heat energy produced by combustion of various alchohols

A

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

31
Q

Neutralisation caloritimatry experiment

A

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

32
Q

Methanol

A

CH3OH

33
Q

Ethanol

A

C2H6O

34
Q

Propanol

A

C3H8O

35
Q

Example of an exothermic reaction

A

The thermit reaction

36
Q

Delta H

A

Temp change

37
Q

Example of an exothermic reaction

A

The thermit reaction

38
Q

Delta H

A

Temp change

Chemsitry (8 decks)

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