P2C19 - Heat energy changes in chemical reactions Flashcards

1
Q

Why do energy changes take place?

A

Because of a chemical reaction

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2
Q

In what examples does a heat energy change happen?

A

Precipitate reactions
Neutralisation reactions
Displacement reactions
Salt dissolved in water

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3
Q

What is a neutralisation reaction?

A

The reaction between an acid and a base

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4
Q

What is a displacement reaction?

A

When a more reactive metal takes the place of a less reactive metal.

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5
Q

Why is salt dissolving in water an example of a chemical reaction where an energy change takes place?

A

Ionic bonds in a salt break.

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6
Q

What is a precipitate reaction?

A

When two solutions react to make an insoluble salt.

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7
Q

What is an exothermic reaction?

A

Energy is transferred to the surroundings

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8
Q

What are some examples of an exothermic reaction?

A

Oxidation
Combustion
Handwarmers
Neutralisation

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9
Q

What is an endothermic reaction?

A

Energy from the surroundings is transferred to the reacting chemicals.

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10
Q

What are some examples of an exothermic reaction?

A

Thermal decomposition
Citric acid + baking soda
Cooling packs

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11
Q

Do exothermic reactions bond make or bond break?

A

Bond make.

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12
Q

Do endothermic reactions bond make or bond break?

A

Bond break.

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13
Q

What is the equation for energy change in a reaction?

A

Energy change = Total bond energies of reactants − Total bond energies of products

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14
Q

What unit is normally used for measuring bond energies?

A

kJ / mol

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15
Q

How do you know if a reaction is endothermic?

A

If the total energy released by forming bonds is LESS than total energy required to break bonds.

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16
Q

How do you know if a reaction is exothermic?

A

If the total energy released by forming bonds is MORE than total energy required to break bonds.

17
Q

What do reaction profiles tell us?

A

The amount of energy contained within the reactants and the products.
The activation energy of a reaction.
The overall energy change in a reaction.

18
Q

What do catalysts do that increase rate of reactions?

A

Lowering the activation energy.