C6 Rates Flashcards

1
Q

What is the rate of a chemical reaction in terms of reactants?

A

How quickly the reactants in a reaction are used up

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2
Q

What is the rate of a chemical reaction in terms of products?

A

How quickly the products in a reaction are formed

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3
Q

What is the formula for a mean rate of reaction in terms of reactants?

A

quantity of reactant used/time taken

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4
Q

What is the formula for a mean rate of reaction in terms of products?

A

quantity of reactant product formed/time taken

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5
Q

How can you measure the quantity of a reactant or product?

A

In grams or in cm³

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6
Q

What are the possible units for rate of reaction?

A

g/s, cm³/s or mol/s (where s is seconds)

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7
Q

How could you measure the rate of a reaction from a graph?

A

Draw a tangent to the curve and calculate the gradient.

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8
Q

What is a tangent line?

A

A straight line that just touches the curve of best fit

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9
Q

How do you calculate a gradient?

A

change in values on y axis ÷ change in values on x axis

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10
Q

What is “collision theory”?

A

The theory that chemical reactions only occur when particles collide with enough energy

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11
Q

What factors can affect the rate of a reaction?

A

Temperature, surface area of a solid, concentration or reactants in solution, pressure of gases

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12
Q

State the effect of increasing the surface area on the rate of a reaction

A

Increases the rate

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13
Q

How can you increase the surface area of a solid?

A

Break it into smaller pieces.

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14
Q

Explain why increasing the surface area increases the rate of a reaction

A

More particles are available to collide, there are therefore more frequent collisions between reactants.

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15
Q

State the effect of increasing the concentration on the rate of reaction

A

Increases

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16
Q

Explain why increasing the concentration increases the rate of reaction

A

More particles in the same volume, therefore more frequent collisions between reactants.

17
Q

State the effect on increasing the pressure of a gas on the rate of reaction

A

Increases

18
Q

Explain why increasing the pressure of a gas increases the rate of a reaction

A

More particles in the same volume, therefore more frequent collisions between reactants.

19
Q

State the effect of increasing the temperature on the rate of reaction

A

Increases

20
Q

What is the activation energy?

A

The energy needed to break bonds to start a reaction

21
Q

Explain why increasing the temperature increases the rate of reaction

A

Increases the kinetic energy of the particles so more frequent collisions, it also increases the number of particles which have the activation energy therefore more collisions result in a reaction.

22
Q

What is a catalyst?

A

Something which changes the rate of a reaction but is not used up in that reaction

23
Q

How do catalysts speed up reactions?

A

They provide another route for the reaction with a lower activation energy.

24
Q

What is a reversible reaction?

A

A reaction which can go from reactants to products but also from products to reactants

25
Q

What chemical symbol represents a reversible reaction?

A

26
Q

If a reaction is exothermic in the forward direction what will it be in the reverse direction?

A

Endothermic

27
Q

Two reactants require 30kJ to turn into products. What energy transfer is involved when the products turn into reactants?

A

30kJ is released

28
Q

What is equilibrium?

A

When the forward and backwards reactions are occurring at the same rate in a closed system

29
Q

How is the amount of reactant changing at equilibrium?

A

It is not changing

30
Q

How is the amount of product changing at equilibrium?

A

It is not changing

31
Q

What is Le Chatelier’s principle?

A

When a reaction at equilibrium is changed, it will seek to counteract that change

32
Q

How does increasing the concentration of a chemical affect the equilibrium position?

A

The equilibrium will shift away from that chemical until it reaches equilibrium again

33
Q

How does increasing the temperature of they system affect the equilibrium position?

A

The equilibrium shifts to the side with the least gas molecules until it reaches equilibrium again

34
Q

How does increasing the pressure of they system affect the equilibrium position?

A

The equilibrium shifts to the endothermic side until it reaches equilibrium again

35
Q

A reaction is exothermic in the forward direction. What will occur if the temperature is increased?

A

The backward reaction will increase as it is endothermic.

36
Q

A reaction is at equilibrium when some product is removed. What will occur?

A

The forward reaction will increase as that will increase the amount of product

37
Q

The reaction below is at equilibrium. What will occur when the pressure is increased? 2H₂(g) + O₂(g) ⇌ 2H₂O(g)

A

The forward reaction will increase as there are fewer molecules on the right.