Rates of Equilibrium Flashcards

1
Q

How to find out the rate of reaction is

A

How quickly reactants are used up as they make products
OR
How quickly products of reaction are made

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2
Q

Three techniques to collect type of data in experiments

A

1) Measure the rate at which the mass of a reaction mixture changes if the reaction gives off a gas
Put on scale, reaction mass decreases if gas is given off
2) Use gas syringe to see increasing volume of gas given off
3) Decreasing light passing through solution = cloudy

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3
Q

Mean rate of reaction equation

A

Mean rate of reaction = quantity of reactant used / time
OR
Quantity of product formed / time

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4
Q

Collision theory

A

Particles need to collide with enough energy to cause a reaction

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5
Q

What is activation energy

A

Minimum amount of energy particles reactants must have before they can react

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6
Q

What affects the rate of reaction and how?

A

Big surface area
Size of pieces of solid affects the rate of the reaction
Particles around solid can only affect surface of reactant
Small lumps or powder have larger surface area surrounded by solution = more particles exposed

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7
Q

Why does raising the temperature increase the rate of reaction?

A

Particles collide more often

Particles collide with more energy

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8
Q

How do particles collide more frequently?

A

Heat substance
Energy transferred to its particles
Particles move around faster
Particles collide more frequently, have more chances to react

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9
Q

How do particles collide with more energy?

A

Particles move around more quickly = have more energy

Collisions are more energetic

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10
Q

Rule of greater collisions

A

An increased proportion of particles exceeding the activation energy has a greater effect on rate than increased frequency of collisions

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11
Q

Effect of concentration

A

More particles of reactants moving around in same volume of solution
More crowded together so more likely they will collide
Increased frequency = faster reaction

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12
Q

Effect of pressure

A

Squashes gas particles more closely together
More particles of gas in given space
Increases chance to collide and react
Produces more frequency collisions

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13
Q

What does a catalyst do

A

Changes rate of reactions
Products do not change
Speeds up rate of a chemical reaction by reducing energy

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14
Q

Catalysts forms

A

Different catalysts needed for different reactions

Usually in form of powders, pellets or fine gauzes = biggest possible SA:V

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15
Q

How catalysts work

A

Do not increase collision frequency
Increase rates of reaction by providing an alternative reaction pathway to products
higher proportion of reactant particles have sufficient energy to react

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16
Q

Advantages and disadvantages of catalysts

A
-expensive
\+cheaper than having to pay for extra energy
\+help environment 
\+save money
-used multiples times
-become poisoned over certain time
17
Q

What happens in a reversible reaction

A

Products of reaction can react to make original reactants

18
Q

What is the reverse reaction if the forward reaction is exothermic?

A

Endothermic

19
Q

Stages of a closed system reaction

A

1) reactants only at start of reaction
2) rate of forward reaction is greater than reverse reaction
3) rate of reverse reaction increases as products build up and rate of forward slows as reactants get used up
4) eventually the rates of the forward and reverse reaction are equal

20
Q

Is there a change in a reaction in reactants and products?

A

No change

21
Q

Equilibrium rule

A

At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction

22
Q

La Chatelier’s Principle and who uses it

A

Change the conditions introduces a system at equilibrium, position of equilibrium shifts to cancel out change
Industrial chemists use it to find the perfect conditions to give as much product as possible

23
Q

What happens if the forward reaction produces more/fewer gas molecules?

A

More molecules of gas:
Increase pressure = decreases amount of products formed
Decrease pressure = increases amount of products formed
Fewer molecules of gas:
Increase pressure = increases amount of products
Decrease pressure = decrease amount of products

24
Q

What happens in a reversible reaction changes the number of gas molecules?

A

Altering pressure affects equilibrium

More molecules of gas on one side of equation

25
Q

Where does equilibrium shift

A

In favour of the reaction that produces fewer gas molecules

E.g. 2NO2 -> N2O4 (shifts to right because only has 1 as big number at front not 2)

26
Q

What happens to the equilibrium is there is an equal number of molecules of gas on both sides?

A

Changing pressure has no effect on the composition of the equilibrium mixture

27
Q

Temperature and equilibrium

A

Closed system = no substances are added or taken away from mixture
Relative amounts of reactants and products in a reversible reaction at equilibrium depend on the temperature

28
Q

What happens if the forward reaction is exothermic/endothermic?

A

Forward reaction is exothermic:
Increase in temperature = decreases the amount of products formed
Decrease in temperature = increases the amount of products formed
Endothermic:
Increase in temperature = increases amount of products formed
Decrease in temperature = decreases the amount of products formed

29
Q

What happens to equilibrium if temperature is increased?

A

Temperature increases = equilibrium shifts to reduce temperature
Endothermic is forward = equilibrium favours reverse reaction (exothermic)