DF1: Thermochemistry Flashcards

1
Q

Define “thermochemistry”

A

The study of energy and heat associated with chemical reactions

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2
Q

Define “exothermic”

A

A reaction that gives out energy and heats surroundings

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3
Q

During an exothermic reaction, are bonds formed/broken?

A

Formed

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4
Q

During an exothermic reaction, is energy released/taken in?

A

Released

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5
Q

Where does energy released from an exothermic reaction go?

A

Its lost to the reaction’s surroundings and heats them up

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6
Q

Is enthalpy change positive/negative for exothermic reactions and why?

A

Negative - products end up with less energy than reactants

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7
Q

Define “endothermic”

A

A reaction that takes in energy and cools the surroundings

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8
Q

During an endothermic reaction, are bonds formed/broken?

A

Broken

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9
Q

Is enthalpy change positive/negative for endothermic reactions and why?

A

Positive - products end up with more energy than reactants

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10
Q

Define “enthalpy change”

A

Amount of energy transferred to and from surroundings

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11
Q

Why are standard conditions used when calculating enthalpy change?

A

They are set conditions which allows us to compare enthalpy changes

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12
Q

What temperature is used in standard conditions?

A

298K

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13
Q

What pressure is used in standard conditions?

A

1atm

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14
Q

What concentration is used in standard conditions?

A

1moldm-3

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15
Q

How do you convert K to degrees C?

A

Minus 273

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16
Q

What are the 4 types of enthalpy change?

A
  • Standard enthalpy change of a reaction
  • Standard enthalpy change of formation
  • Standard enthalpy change of combustion
  • Standard enthalpy change of neutralisation
17
Q

Define “standard enthalpy change of a reaction”

A

Enthalpy change when one mole of matter is transformed by a chemical reaction under standard conditions

18
Q

Define “standard enthalpy change of a formation”

A

Enthalpy change when 1 mole of a compound is formed from its elements in their standard states, under standard conditions

19
Q

Define “standard enthalpy change of a combustion”

A

Enthalpy change when 1 mole of a substance is completely burned in oxygen, under standard conditions

20
Q

Define “standard enthalpy change of a neutralisation”

A

Enthalpy change when acid reacts with alkali to form 1 mole of water under standard conditions

21
Q

Define “standard states”

A

A substance’s most stable state under standard conditions

22
Q

Are all combustion reactions positive/negative and why?

A

Negative because they are all exothermic

23
Q

What is the formula for calculating enthalpy change?

A

q=m x c x change in T

24
Q

What is the specific heat capacity of water?

A

4.18Jg-1k-1

25
Q

How does a bomb calorimeter work?(2)

A
  • Fuel is ignited electrically and burns oxygen inside the pressurised vessel
  • Energy is transferred to the surrounding water
26
Q

What is measured in a bomb calorimeter?

A

Temperature rise

27
Q

How is the experiment conducted in a bomb calorimeter?

A

At a constant volume in a closed container

28
Q

Why is the fuel in a bomb calorimeter burnt under pressure?

A

To increase the number of successful collisions leading to complete combustion of the sample

29
Q

Why is a bomb calorimeter more accurate than a simple calorimeter?

A

Low heat losses