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GCSE Chemistry > C8 > Flashcards

C8 Flashcards

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1
Q

What is the rate of a chemical reaction?

A

How fast the reactants are changed into products

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2
Q

What is the slowest chemical reaction?

A

Rusting of iron

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3
Q

How to find the speed of a reaction?2 ways

A
  • record the amount of product formed

- the amount of reactant used up over time.

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4
Q

What type of line would it be for a quick reaction?

A

A steep line

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5
Q

What does the rate of reaction depend on?

A
  • temperature
  • concentration of solution or pressure of gas
  • surface area
  • presence of a catalyst
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6
Q

How collisions affect the rate of reactions?

A
  • collision frequency (how often they collide) more collisions means a faster reaction.
  • energy transferred during a collision. Enough energy must be there for a collision to be successful
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7
Q

What is activation energy?

A

Minimum amount of energy that particles need to react. Particles need that much energy to break bonds in the reactants and start the reaction.

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8
Q

How does temperature effect the rate of reaction?

A

-increase , will increase the rate as particle move faster as have more energy (enough for reaction to happen) and will collide more frequently

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9
Q

How concentration or pressure affects the rate of reaction?

A
  • increase in conc. will increase the rate of reaction as it mean more particles colliding in the same volume
  • if the pressure of gas is increased , the same applies
  • both of these increasing makes collisions between particles more frequent
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10
Q

How the surface area affects the rate of reaction?

A
  • if there is a solid . Breaking it up into smaller bits will increase the surface area to volume ratio.
  • same volume of solid will have more area for particles to collide amd so collisions will happen more frequently
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11
Q

How catalysts effect the rate of reaction?

A

They decrease activation energy needed for a reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy.

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12
Q

What is a catalyst?

A

Substance that speeds up a chemical reaction, without it being used up itself. It isn’t part of the overall equation. Different reactions need different catalysts.

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13
Q

What are enzymes?

A

Biological catalysts

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14
Q

Equations for the mean rate of reaction?

A

Quantity of reactant used / time taken

Quantity of product formed / time taken

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15
Q

How can the rate of a reaction be found?

A

Measuring the quantity of a reactant used or the quantity of the product formed over time.

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16
Q

How can the quantity of a reactant be measured?

A

Mass( gram) or volume (cm cubed)

17
Q

What is the unit for rate of reaction?

A

g/s or cm ^3 /s

18
Q

How to calculate the mean reaction from a graph?

A

Find the time taken and the volume or mass of the product and draw lines up to see what is the difference then divide thta by time taken.

19
Q

Steps to draw a tangent to find the reaction rate at a particular point?

A
  • position ruler on a given point
  • adjust ruler so space is equal on both sides
  • make tangent
  • find the gradient of the line
20
Q

How to work out the gradient of a line?

A

Change in y / change in x

21
Q

What is a reversible reaction?

A

The products of the reaction can react to produce the original reactants .

22
Q

How do you know if a reaction is reversible ?

A

If there is two arrows pointing opposite ways on top of each other.

23
Q

How do reversible reactions react?

A

1) as reactant react , concentration of the forward reaction will slow down , so as more products are made the backwards reaction will speed up .
2) eventually it will be going at exactly the same rate which is the equilibrium

24
Q

What is the equilibrium?

A

When a reversible reaction happens occurs in apparatus which prevent the escape of products or reactants, equilibrium is reached when the forward and reverse reactions occur at exactly the same time.

25
Q

What happens if a reversible reaction is exothermic in one direction?

A

It is endothermic in the other directions.

For example :
Hydrated copper is endothermic forming copper sulfate + water but is exothermic on the way back .

26
Q

How can the directions of a reversible reaction be changed?

A

Heating and cooling for example heating ammonium chloride will reach ammonia + hydrogen chloride and cooling will go the other way

27
Q

Examples of endothermic and exothermic reversible reaction?

A

Hydrated copper sulfate reversible anhydrous copper sulfate

—–> endothermic

28
Q

What are la chanteliers principles?

A

If you change the conditions of a reversible reaction at equilibrium , the system will try to counteract that change. It can be used to predict the effect of any changes you make to a reaction

29
Q

What happens if the temperature increases in a reversible reaction?

A
  • relative amount of products at equilibrium increases for endothermic reaction
  • relative amount of products at the equilibrium decreases for exothermic
30
Q

What happens to a reversible reaction if the temperature increases?

A
  • relative amount of products at equilibrium decreases for endothermic
  • relative amount of products at equilibrium increases for exothermic
31
Q

What are the effects of changing concentration of a reversible reactants products or reactants?

A

System no longer at equilibrium and the concentration of all substances will change until at the equilibrium again.

32
Q

What happens in a reversible reaction if the concentration of the reactant increases?

A

More products will be formed until equilibrium is reached

33
Q

What happens if the concentration of a product is decreased in a reversible reaction?

A

More reactants will react until equilibrium is reached again

34
Q

What state does pressure affect?

A

Gaseous state

35
Q

What will happen if there is an increase in pressure in a reversible reaction ?

A

The equilibrium position will shift towards the side with smaller number of moles as shown by the symbol equation for that reaction

36
Q

What will happen if there is a decrease in pressure in a reversible reaction?

A

Causes the equilibrium to shift towards the side with the large number of moles as shown by the symbol equation.

GCSE Chemistry (14 decks)

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