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IGCSE Chemistry > Chemical rates & energetics > Flashcards

Chemical rates & energetics Flashcards

Collision theory

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1
Q

Define chemical reaction

A

Making of new products from the rearrangement of reactants

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2
Q

Define rate of reaction

A

How quickly a reactant is used up or how quickly product is formed

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3
Q

Define high rate of reaction

A

Reactants turn into products quickly

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4
Q

Define low rate of reaction

A

Reactants turn into products slowly

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5
Q

What particles need to collide [2]

A

1) In correct orientation
2) Enough energy

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6
Q

Define successful collisions

A

When reactant particles collide and turn into products.

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7
Q

Define activation energy

A

Smallest amount of energy required for reaction to occur

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8
Q

What is a reactant

A

What you start with in a reaction

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9
Q

What is a product

A

What you end with in a reaction

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10
Q

How does the amount of reactant particles change throughout a reaction? [3]

A

1) Lots of reactant particles at the beginning, steep line due to lots of reactions
2) Rate of reaction slows down as there is now a mixture of reactant and products particles
3) The reactions are finished line is flat and theres only product particles with no reactant particles.

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11
Q

Mean rate of reaction formula (g/s)

A

Mass (g) /time taken (s)

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12
Q

Mean rate of reaction formula (cm3/s)

A

Volume (cm3) / time taken (s)

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13
Q

How is gas collected?

A

A gas syringe

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14
Q

What does it mean if gas is collected quickly

A

Rate of reaction is high

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15
Q

Define concentration

A

Quantity of subtance in a set volume

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16
Q

Explain the effect that increasing the concentration of something has on the rate of reaction

A

1) Higher concentration means high rates of reaction
2) More particles in the same space due to higher concentration
3) more frequent collisions means more successful collisions

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17
Q

Increasing temperature increases both

A

1) Frequency of collisons
2) The number of collisions with enough energy to react

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18
Q

Factors effectig rate of reaction [7]

A

1) Concentration, increase amount of particles
2) Pressure, increase gas particles
3) Reduce volume, less distance
4) Temperature, increase kinetic energy of particles
5) Surface area more particles are exposed on the outside
6) Catalyst will lower the activation energy
7) Biological catalyst dont denature in chemistry

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19
Q

What 2 things happen when chemical reaction takes place

A

1)New products- chemical change
2) Change in heat energy

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20
Q

How to break bonds

A

Energy is absorbed

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21
Q

How to form bonds

A

Energy is released

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22
Q

Endothermic reactions definition

A

Energy is absorbed from the surroundings, the temperature of the surroundings decrease. It gets colder to convert thermal into chemical energy to break bonds

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23
Q

Exothermic reactions definition

A

Heat energy is produced, temperature of the sourroundings increases

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24
Q

More energy is released compaired to the energy…

A

More energy is released compaired to the energy needed to breakt the catalyst

25
Q

Compare the speeds of radio waves and visible light in a vacuum:

A

Radio waves and visible light have the same speed in a vacuum because all EM waves travel at the speed of light

26
Q

What are bonds?

A

C = C, H - H
they are lines between molecules

27
Q

How to calculate number of bonds of H - O - H

A

H - O - H
2 bonds

28
Q

Does O = c = O count as 4 bonds

A

FALSEE!!!
It is a covalent double bond so its still 1 bond
In total it has 2 bonds

29
Q

Law of break and making bond

A

Energy required to break bond is equal to energy required to make bond

30
Q

Overall energy change formula

A

Energy needed to break the bonds (reactant) - energy released as bonds are made (products)

31
Q

Explain successful and unsuccessful collisions

A

1) Successful means that the reactant particles collide and rearrange to form the products
2) Unsuccessful means the reactant particles just bounce off each other and remain unchanged

32
Q

Enthalpy change (ΔH)

A

= Energy taken in - Energy given out

33
Q

Define enthaply

A

a measure of the total heat of reaction of a chemical reaction

34
Q

Reversible reaction definition

A

Means the reaction goes back and forth constantly

35
Q

Define equilibrium

A

Forward and backward reaction are taking place at the same rate at the same time

36
Q

Define closed system

A

No substance can enter or exit

37
Q

Le Chatelier principle

A

If a change is made to the conditions of the system at equilibrium, then the position of the equilibrium moves to oppose that change in conditions
(If u make the system hot it doesnt like it and trys to cool)

38
Q

Equilibrium lies to the left

A

More reactants than products in the mixture of chemicals

39
Q

Equilibrium lies to the right

A

More products than reactants in the mixture of chemicals

40
Q

Define catalyst [2]

A

1) A substance that speeds up reaction
2) Remains unchanged chemically

41
Q

On the right/forward it is exothermic/endothermic

A

exothermic

42
Q

On the left/backward direction it is exothermic/endothermic

A

Endothermic

43
Q

As temperature increase which direction does it shift to

A

endothermic to try to cool the system

44
Q

As temperature decrease which direction does it shift to

A

Exothermic to heat up the system

45
Q

The haber process

A

The method of making ammonia

46
Q

Ammonia equation

A

N2(g) + 3H2(g) <–> 2NH3(g)

47
Q

Reaction conditiosn for the haber process

A

1) 450c, 200 atm, and iron catalyst

48
Q

Why does the conditions for ammonia not use a lower temperature?

A

Low temperatures reduce the rate of reaction, so scientist compromise between yeild and rates

49
Q

ammonium salts reacts with an alkali to produce: ammonia, water and a salt T or F

A

T

50
Q

a really high temperature is used to speed up the reaction for the haber process

A

True

51
Q

Pressure can be changed in 2 ways

A

Make the space smaller
Add more particles

52
Q

Rates of reaction equation include unit

A

change in mass over time g/s
Change in volume over time
cm3/s

53
Q

Hydration of salts

A

Some chemical equation can be reversed by adding water or by heating to remove water by evporation

54
Q

What is the formula for vanadium(V) oxide

A

V2O5

55
Q

CaCO3 reacts with HCL to form CO2 state 3 ways to decrease the rate of reaction

A

1) Increase particle size
2) Decrease concentration
3) Decrease temperature

56
Q

Explain the term equlibrium mixture

A

In a reversible reaction, the rate of the forward reaction is equal to the reverse

57
Q

^H meaning

A

Triangle and a H is change in enthalpy/ change in energy

58
Q

Explain conditions of the haber process

A

1) 450c is used to increase rates of reaction, it causes the equilibrium to shift left so it is a compromise.
2) 200 atm is used to increase rates of reaction as distance between molecules decrease, it increases yeild of ammonia
3) Iron catalyst is used to increase rates of reaction by lowering activation energy

IGCSE Chemistry (10 decks)

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