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Chemistry > The Rate and Extent of Chemical Changes C6 > Flashcards

The Rate and Extent of Chemical Changes C6 Flashcards

1
Q

What is the rate of a chemical reaction?

A

The rate of a chemical reaction is how fast the reactants are changed into products.

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2
Q

What is one of the slowest chemical reactions?

A

The rusting of iron is one of the slowest chemical reactions.

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3
Q

What are examples of slow reactions?

A

Other slow reactions include chemical weathering like acid rain damage to limestone.

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4
Q

What is an example of a moderate speed reaction?

A

An example of a moderate speed reaction would be magnesium reacting with an acid to produce bubbles.

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5
Q

What characterizes fast reactions?

A

Burning is a fast reaction, but explosions are even faster and release a lot of gas.

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6
Q

How can you find the speed of a reaction?

A

You can find the speed of a reaction by recording the amount of product formed or the amount of reactant used up over time.

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7
Q

What does a steeper line on a reaction graph indicate?

A

The steeper the line on the graph, the faster the rate of reaction.

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8
Q

What happens to the line on a reaction graph over time?

A

Over time, the line becomes less steep as the reactants are used up.

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9
Q

What does collision theory explain?

A

Collision theory explains how different factors affect the rate of reaction.

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10
Q

What is activation energy?

A

The minimum amount of energy that particles need to react is called the activation energy.

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11
Q

What factors increase the number of collisions in a reaction?

A

The collision frequency of reacting particles increases the number of collisions, making the reaction faster.

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12
Q

What is a successful collision?

A

A successful collision is one that results in the particles reacting to form products.

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13
Q

What are the four factors affecting the rate of reaction?

A

1) Temperature.
2) Concentration of a solution or pressure of gas.
3) Surface area.
4) Presence of a catalyst.

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14
Q

How does increasing temperature affect the rate of reaction?

A

Increasing temperature causes particles to move faster, leading to more frequent collisions and more energetic collisions.

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15
Q

How does increasing concentration or pressure affect the rate of reaction?

A

Higher concentration means more particles in the same volume, while higher pressure means the same number of particles in a smaller space, both increasing collision frequency.

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16
Q

How does increasing surface area affect the rate of reaction?

A

Breaking a solid into smaller pieces increases its surface area to volume ratio, allowing for more frequent collisions.

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17
Q

What is a catalyst?

A

A catalyst is a substance that speeds up a reaction without being used up in the reaction itself.

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18
Q

How do catalysts increase the rate of reaction?

A

Catalysts decrease the activation energy needed for the reaction by providing an alternative reaction pathway with a lower activation energy.

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19
Q

What are enzymes?

A

Enzymes are biological catalysts that catalyse reactions in living organisms.

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20
Q

What happens to the activation energy when a catalyst is used?

A

The activation energy is lowered when a catalyst is present.

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21
Q

Which reaction would have the fastest rate: powdered magnesium with water or hydrochloric acid with excess ethanoic acid?

A

Hydrochloric acid with excess ethanoic acid would have the fastest rate due to higher concentration.

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22
Q

What are the two ways to observe the rate of a reaction?

A

The rate of a reaction can be observed by how quickly the reactants are used up or how quickly the products are formed.

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23
Q

What are the units for measuring the rate of a reaction?

A

The units for rate may be in cm/s, g/s, or mol/s.

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24
Q

What is the first method of measuring the rate of a reaction?

A

1) Precipitation and Colour Change: You can record the visual change in a reaction if the initial solution is transparent and the product is a precipitate which clouds the solution.

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25
Q

How can you measure the time taken for a mark to disappear in a reaction?

A

You can observe a mark through the solution and measure how long it takes for the mark to disappear.

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26
Q

What is the second method of measuring the rate of a reaction?

A

2) Change in Colour: You can time how long it takes for the solution to lose (or gain) its colour.

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27
Q

What is a disadvantage of using visual methods to measure reaction rates?

A

The results are subjective; different people might not agree on the exact point when the mark disappears or the solution changes colour.

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28
Q

What is the third method of measuring the rate of a reaction?

A

3) Mass (Usually Gas Given Off): As the gas is released, the mass disappearing is measured on the balance.

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29
Q

How can the volume of gas produced be measured?

A

1) Using a gas syringe to measure the volume of gas given off during a reaction.

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30
Q

What does a quicker reading on the balance indicate?

A

The quicker the reading on the balance drops, the faster the reaction.

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31
Q

What is the most accurate method described for measuring reaction rates?

A

The mass balance method is the most accurate because it provides precise measurements.

32
Q

What is a potential hazard when using a gas syringe?

A

If the reaction is too vigorous, you can easily blow the plunger out of the end of the syringe.

33
Q

What is an example of a reaction that produces gas?

A

The reaction between solid NaCO and aqueous HCl releases CO2 (a gas).

34
Q

What is turbidity in relation to a solution?

A

Turbidity refers to the cloudiness of a solution, which changes during a reaction.

35
Q

What is the first step in the reaction with magnesium and dilute hydrochloric acid?

A

Start by adding a set volume of dilute hydrochloric acid to a conical flask and carefully place on a mass balance.

36
Q

What should you do after adding magnesium ribbon to the acid?

A

Quickly plug the flask with cotton wool.

37
Q

What should be recorded during the reaction?

A

Start the stopwatch and record the mass on the balance at regular intervals.

38
Q

What is the effect of changing the concentration of hydrochloric acid on the reaction rate?

A

The results show the effect of decreasing the concentration of HCl on the rate of reaction.

39
Q

What is the procedure for the reaction between sodium thiosulfate and hydrochloric acid?

A

Start by adding a set volume of dilute sodium thiosulfate to a conical flask, place it on a piece of paper with a black cross, add dilute HCl, and start the stopwatch.

40
Q

What should be done to visualize the reaction between sodium thiosulfate and HCl?

A

Watch the black cross disappear through the cloudy sulfur and time how long it takes to go.

41
Q

What should be kept constant in the experiments?

A

Variables such as the amount of magnesium ribbon and the volume of acid used should be kept the same each time.

42
Q

What is the relationship between concentration and reaction time?

A

The higher the concentration, the quicker the reaction, and therefore the less time it takes for the mark to disappear.

43
Q

What safety precaution should be taken during the experiment?

A

The experiment should be carried out in a well-ventilated place due to the release of sulfur dioxide.

44
Q

What type of graph can be plotted from the results of the sodium thiosulfate and HCl reaction?

A

You could draw a graph of concentration against 1/time which will give you an approximate rate.

45
Q

What does a rate of reaction graph show?

A

A rate of reaction graph shows the amount of product formed or amount of reactant used up on the y-axis and time on the x-axis.

46
Q

How do you calculate the mean rate of reaction from a graph?

A

To find the mean rate for the whole reaction, work out the overall change in the y-value and divide this by the total time taken for the reaction.

47
Q

How can you find the mean rate of reaction between two points in time?

A

You can find the mean rate of reaction between any two points in time by calculating the change in y over the change in x.

48
Q

What is the formula for mean rate of reaction?

A

Mean rate of reaction = change in y / change in x.

49
Q

How do you find the rate of reaction at a particular point in time?

A

To find the rate of reaction at a particular point in time, draw a tangent to the curve at that point and calculate the gradient of the tangent.

50
Q

What is the process to draw a tangent to a curve?

A

1) Position a ruler at the point of interest. 2) Adjust the ruler until the space between the ruler and the curve is equal on both sides. 3) Draw a line along the ruler to create the tangent.

51
Q

What is the rate of reaction at 3 minutes if the gradient is calculated?

A

The rate of reaction at 3 minutes was 0.27 g/min.

52
Q

What should you do if the reaction finishes?

A

If asked to find the mean rate of reaction for the whole reaction, remember that the reaction finishes as soon as the line on the graph goes flat.

53
Q

What happens in a reversible reaction?

A

The products can react to form the reactants again.

54
Q

What occurs as reactants in a reversible reaction react?

A

Their concentrations fall, slowing down the forward reaction.

55
Q

What happens as more products are made in a reversible reaction?

A

The concentrations of products rise, speeding up the backward reaction.

56
Q

What is equilibrium in a reversible reaction?

A

It is when the forward and backward reactions occur at the same rate.

57
Q

What is a closed system in the context of reversible reactions?

A

A closed system means that none of the reactants or products can escape and nothing else can get in.

58
Q

Does equilibrium mean equal amounts of reactants and products?

A

No, equilibrium does not mean the amounts of reactants and products are equal.

59
Q

What does it mean if equilibrium lies to the right?

A

The concentration of products is greater than that of the reactants.

60
Q

What does it mean if equilibrium lies to the left?

A

The concentration of reactants is greater than that of the products.

61
Q

What factors affect the position of equilibrium?

A

Temperature, pressure (for gases), and concentration of reactants and products.

62
Q

What is the nature of reversible reactions regarding endothermic and exothermic processes?

A

If a reaction is endothermic in one direction, it will be exothermic in the other.

63
Q

What happens when blue hydrated copper(II) sulfate is heated?

A

It drives the water off and leaves white anhydrous copper(II) sulfate powder.

64
Q

What occurs when water is added to anhydrous copper sulfate?

A

It forms blue crystals of hydrated copper sulfate again.

65
Q

What is dynamic equilibrium?

A

It involves lots of activity, but with no overall effect on concentrations.

66
Q

What is Le Chatelier’s Principle?

A

Le Chatelier’s Principle states that if you change the conditions of a reversible reaction at equilibrium, the system will try to counteract that change.

67
Q

How can Le Chatelier’s Principle be used?

A

It can be used to predict the effect of any changes you make to a reaction system.

68
Q

What happens to equilibrium when temperature is decreased?

A

If you decrease the temperature, the equilibrium will move in the exothermic direction to produce more heat.

69
Q

What happens to equilibrium when temperature is increased?

A

If you raise the temperature, the equilibrium will move in the endothermic direction to try and decrease it.

70
Q

How does pressure affect equilibrium involving gases?

A

Changing the pressure only affects an equilibrium involving gases.

71
Q

What happens to equilibrium if pressure is increased?

A

If you increase the pressure, the equilibrium tries to reduce it by moving in the direction where there are fewer molecules of gas.

72
Q

What happens to equilibrium if pressure is decreased?

A

If you decrease the pressure, the equilibrium tries to increase it by moving in the direction where there are more molecules of gas.

73
Q

How does changing concentration affect equilibrium?

A

If you change the concentration of either the reactants or the products, the system will no longer be at equilibrium.

74
Q

What happens if the concentration of reactants is increased?

A

If you increase the concentration of the reactants, the system tries to decrease it by making more products.

75
Q

What happens if the concentration of products is decreased?

A

If you decrease the concentration of products, the system tries to increase it again by reducing the amount of reactants.

76
Q

How does an increase in pressure affect the reaction N2 + 3H2 ⇌ 2NH3?

A

If you increase the pressure, the equilibrium shifts to the right, producing more NH3.

77
Q

What is the significance of control in reversible reactions?

A

Control in reversible reactions is crucial for profitability in industry.

Chemistry (10 decks)

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