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Chemistry > Unit 3: Chemistry in Society > Flashcards

Unit 3: Chemistry in Society Flashcards

1
Q

When has a reaction reached equilibrium?

A

A reaction has reached equilibrium when the rate of the forward reaction equals the rate of the reverse reaction.

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2
Q

If the forward reaction is favoured…?

A

Equilibrium moves to the right.

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3
Q

If the backward reaction is favoured…?

A

Equilibrium moves to the left.

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4
Q

An increase is temperate favours an…?

A

Endothermic reaction.

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5
Q

A decrease in temperature favours an…?

A

Exothermic reaction.

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6
Q

What happens to a reaction when temperature is increased?

A

Causes the equilibrium to move to the right. The forward reaction takes in energy so it moves to the right producing more products and less reactants.

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7
Q

What happens to a reaction when temperature is decreased?

A

Causes the equilibrium to move to the left. The backward reaction gives out energy so it moves to the right producing more reactants and less products.

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8
Q

What does increasing the concentration do?

A

Causes the equilibrium to move to use up the chemical.

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9
Q

What does decreasing the concentration do?

A

Causes the equilibrium to move to form the chemical.

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10
Q

What does increasing the pressure do?

A

Increasing the pressure will cause the equilibrium to move to decrease the pressure. The equilibrium will move to decrease the number of gas particles.

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11
Q

What does decreasing the pressure do?

A

Decreasing the pressure will cause the equilibrium to move to increase the pressure. The equilibrium will move to increase the number of gas particles.

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12
Q

What does a catalyst do to equilibrium?

A

The use of a catalyst does not change the equilibrium it only enables the position of the equilibrium to be reached more quickly.

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13
Q

What is the enthalpy of combustion?

A

The enthalpy of combustion of a substance is the amount of energy given out when one mole of a substance burns in excess oxygen.

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14
Q

What is the enthalpy of solution?

A

The energy change when one mole of a substance is dissolved in water (can be positive or negative).

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15
Q

What is Hess’s law?

A

The overall enthalpy change for a reaction is the same whichever route is taken.

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16
Q

What is the molar bond enthalpy for a diatomic molecule to break?

A

It is the energy required to break one mole of bonds.

17
Q

What is the energy required for a diatomic molecule to make a bond?

A

The energy required to make one mole of bonds is the same as the bond enthalpy but has a negative value.

18
Q

Oxidation is…Reduction…Redox…

A

O=loss of electrons, R=gain of electrons, Redox= at the same time

19
Q

What does a substance which is oxidized do?

A

The substance that is oxidised donates its electrons to the substance that is reduced.

20
Q

What do oxidising agents do?

A

They remove electrons from other chemicals forcing them to lose electrons. These agents are reduced in the reaction.

21
Q

What do reducing agents do?

A

They donate electrons to other chemicals causing them to become reduced. These agents are oxidised in the reaction.

22
Q

What do substances with low electronegativities (metals) do?

A

They form ions by losing electrons (oxidation) and act as redeucing agents.

23
Q

What do substances with high electronegativities (non-metals) do?

A

They form ions by gaining electrons (reduction) and act as oxidising agents.

24
Q

Uses of strong oxidisng agents?

A

Hydrogen peroxide- bleach clothes and hair, effective at breaking down colour compounds.

25
Q

What is chemical analysis?

A

Industry use of checks on purity of reactants and products.

26
Q

What is chromatography?

A

It separates compounds according to their relative affinity for the “mobile” and “stationary” phase.

27
Q

What is he “mobile” phase?

A

Liquid or gas-molecule size ans polarity may affect their solubility.

28
Q

What is the “stationary” phase?

A

Paper, silica gel, inert (unrecative solid) packing material.- size and polarity of compounds also affect this phase.

29
Q

What is TLC?

A

Thin layer chromatography. Compounds are identified by the distance they have moved from the starting point.

30
Q

What is column chromatography?

A

Method that identifies by how quickly hey travel through tr solid phase.

Chemistry (2 decks)

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