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Physical Week 4 Flashcards

Energetics

1
Q

What is the Maxwell-Boltzmann Distribution curve?

A

Maxwell-Boltzmann Distribution is a graph that represents the distribution of energies among particles in a system, particularly in gases. It shows the number of particles with different energy levels.

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2
Q

What is the activation energy?

A

Activation Energy is the minimum energy required for a collision between particles to result in a chemical reaction. It is the energy barrier that must be overcome for the reaction to occur.

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3
Q

What is a species (in the context of chemistry)?

A

Species, in the context of chemistry, refers to any type of particle involved in a chemical reaction. It can be a molecule, an ion, or even a free radical.

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4
Q

What is the collision theory?

A

Collision Theory is a concept in chemistry that explains how the likelihood of a chemical reaction occurring depends on the collision energy and collision orientation of the reacting particles. According to Collision Theory, for a reaction to occur, the particles must collide with each other in the right way and with enough energy to break the existing bonds and form new ones.

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5
Q

What is a catalyst?

A

A Catalyst is a substance that increases the rate of a chemical reaction by lowering the activation energy required for the reaction to occur. It does not get consumed in the reaction and can be used repeatedly.

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6
Q

How can the speed of a reaction be increased according to the Maxwell-Boltzmann distribution?

A

By adjusting the temperature to change the curve’s shape and using a catalyst to shift the activation energy to the left

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7
Q

What is required for a reaction to occur?

A

For a reaction to occur, particles need to collide with energy equal to or greater than the activation energy.

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8
Q

What is required for two particles to react?

A

For two particles to react, they need to come into contact, collide in the right way, and have enough energy to break bonds.

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9
Q

What do collision theory and Maxwell-Boltzmann distribution explain?

A

Collision theory and Maxwell-Boltzmann distribution explain the factors necessary for a collision to result in a reaction: collision energy and collision orientation.

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10
Q

Why do gentle collisions lack sufficient energy to initiate bond breaking?

A

Gentle collisions lack sufficient energy to initiate bond breaking because they have less energy than the activation energy required.

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11
Q

What does the area under the curve in the Maxwell-Boltzmann Distribution graph represent?

A

The area under the curve in the Maxwell-Boltzmann Distribution graph represents the total number of particles present.

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12
Q

What are the two ways to speed up a reaction according to the Maxwell-Boltzmann distribution?

A

Adjusting the temperature to change the curve’s shape and shifting the activation energy to the left by using a catalyst

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13
Q

How can a reaction be sped up?

A

A reaction can be sped up by adjusting the temperature to change the curve’s shape or by using a catalyst to shift the activation energy to the left.

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14
Q

What is the role of activation energy in a chemical reaction?

A

Activation energy is the minimum energy which particles need to collide to start a reaction. It acts as a hurdle for the reaction, only collisions with energies equal to or higher than this hurdle lead to a reaction.

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15
Q

How does temperature affect the ROR?

A

Temperature is a measure of the average kinetic energy of particles in a substance. In the context of reaction rates, increasing the temperature generally leads to an increase in the rate of reaction.

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16
Q

How does concentration affect the ROR?

A

Concentration refers to the amount of a substance present in a given volume. In the context of reaction rates, increasing the concentration of reactants generally accelerates the reaction.

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17
Q

What are reaction rates?

A

Reaction rates refer to the speed at which a chemical reaction occurs. It is defined as the change in concentration of a substance per unit of time.

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18
Q

How does pressure affect the ROR?

A

Pressure is the force exerted per unit area. In the context of reaction rates, increasing the pressure in a reaction involving gases can lead to an increase in the rate of reaction.

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19
Q

How does a catalyst affect the ROR?

A

Catalysts are substances that increase the rate of a chemical reaction without being consumed in the process. They achieve this by providing an alternative pathway or mechanism with a lower activation energy.

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20
Q

What is activation energy?

A

Activation energy is the minimum amount of energy required for a chemical reaction to occur. Collisions between particles only result in a reaction if they have enough energy to overcome the activation energy barrier.

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21
Q

What does the Maxwell-Boltzmann distribution graph show?

A

The Maxwell-Boltzmann distribution graph shows that only particles with energies above the activation energy can react.

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22
Q

How does increasing the concentration of reactants affect the reaction rate?

A

Increasing the concentration of reactants accelerates the reaction by increasing the likelihood of collisions between particles.

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23
Q

How do higher concentrations and pressures affect the occurrence of collisions among particles?

A

Higher concentrations and pressures lead to more frequent collisions among particles, resulting in a higher occurrence of effective collisions.

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24
Q

What is required for reactions to occur?

A

Reactions only occur when particles collide with enough energy, known as activation energy.

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25
Q

What is the relationship between gas pressure and its concentration?

A

Pressure is directly proportional to concentration. Increasing gas pressure is like increasing its concentration.

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26
Q

What happens to the reaction rate when the temperature increases?

A

A significantly larger proportion of particles have energy greater than the activation energy, leading to an increase in the frequency of successful collisions, thus increasing the reaction rate.

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27
Q

How do catalysts increase reaction speeds?

A

Catalysts increase reaction speeds by offering an alternate pathway with a lower activation energy, facilitating the occurrence of reactions.

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28
Q

How can the speed of a reaction be increased according to the Maxwell-Boltzmann distribution graph?

A

By increasing the temperature to have a higher number of highly energetic particles present at any given moment, with energies equal to or greater than the activation energy.

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29
Q

What is the role of activation energy in a reaction?

A

Only particles in the region to the right of the activation energy have enough energy to react when they collide.

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30
Q

What is the effect of increasing the pressure in reactions involving gases?

A

Increasing the pressure in reactions involving gases increases the reaction rate.

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31
Q

How does temperature affect equilibrium?

A

Temperature refers to the measure of the average kinetic energy of the particles in a substance. In the context of Le Chatelier’s Principle, changing the temperature of a reaction can affect the position of equilibrium.

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32
Q

What is a catalyst and how does it affect equilibrium?

A

A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the reaction. In the context of Le Chatelier’s Principle, adding a catalyst to a reaction does not change the position of equilibrium.

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33
Q

What is Le Chatelier’s principle?

A

Le Chatelier’s Principle is a principle in chemistry that states that when an external condition is changed, the equilibrium position of a chemical reaction will shift to counteract the change. It explains the effects of changing concentration, pressure, or temperature on the equilibrium state of a reaction.

34
Q

What is chemical equilibrium?

A

Chemical equilibrium refers to the state in a chemical reaction where the forward and backward reactions occur at equal rates, and the concentrations of reactants and products remain constant over time. It is a dynamic state where the rate of the forward reaction is equal to the rate of the backward reaction.

35
Q

What is concentration and how does it affect equilibrium?

A

Concentration refers to the amount of a substance present in a given volume or space. In the context of Le Chatelier’s Principle, changing the concentration of a substance in a chemical reaction can affect the position of equilibrium.

36
Q

How will an exothermic reaction affect equilibrium?

A

In the context of Le Chatelier’s Principle, when dealing with exothermic reactions, increasing the temperature will shift the equilibrium position in the direction that absorbs heat, while decreasing the temperature will shift the equilibrium position in the direction that releases heat.

37
Q

How will an endothermic reaction affect equilibrium?

A

In the context of Le Chatelier’s Principle, when dealing with endothermic reactions, increasing the temperature will shift the equilibrium position in the direction that releases heat, while decreasing the temperature will shift the equilibrium position in the direction that absorbs heat.

38
Q

What is pressure and how does it affect equilibrium?

A

Pressure refers to the force exerted by a gas on the walls of its container. In the context of Le Chatelier’s Principle, changing the pressure of a gas reaction can affect the position of equilibrium.

39
Q

How does increasing the temperature in an exothermic reaction affect the equilibrium position?

A

In an exothermic reaction, increasing the temperature will shift the equilibrium position to lower the temperature.

40
Q

How does changing the concentration of a substance in a reaction affect the equilibrium position?

A

Changing the concentration of a substance in a reaction will cause the equilibrium position to shift in order to oppose the change.

41
Q

What happens to the pressure when there are more particles in a container?

A

Increasing the number of particles in a container increases pressure.

42
Q

What are the key features of dynamic equilibrium?

A

In dynamic equilibrium, the forward and backward reactions occur at equal rates and the amounts of reactants and products remain constant.

43
Q

How does adding a catalyst affect the position of equilibrium?

A

Adding a catalyst does not affect the position of equilibrium.

44
Q

What does Le Chatelier’s Principle explain?

A

Le Chatelier’s Principle explains how the equilibrium position of a chemical reaction shifts to counteract changes in external conditions.

45
Q

What happens to the equilibrium position when the temperature is decreased in an exothermic reaction?

A

Decreasing the temperature will shift the equilibrium position to raise the temperature.

46
Q

According to Le Chatelier’s principle, how does a system react to reduce pressure?

A

Le Chatelier’s principle states that a system will react in a way that reduces pressure.

47
Q

What happens to the position of equilibrium when the temperature is increased?

A

Increasing the temperature favors the endothermic reaction.

48
Q

What is a percentage error?

A

Percentage error is a measure of the accuracy of a measurement or calculation, expressed as a percentage of the difference between the measured or calculated value and the true or accepted value. In the context of measuring heat changes in experiments, percentage error is used to evaluate the accuracy of the temperature change measured by a thermometer.

49
Q

What is the equilibrium constant?

A

In Chemistry, the equilibrium constant Kc is a constant that indicates the position of equilibrium for a reaction at a specific temperature. It remains unchanged unless the conditions of the reaction, and thus the equilibrium position, are altered.

50
Q

What is specific heat capacity?

A

Specific heat capacity, is the amount of heat energy required to raise the temperature of 1 gram of a substance by 1 degree Kelvin or Celsius. It is denoted by the symbol ‘c’ or ‘s’ and is measured in joules per gram per degree Kelvin or Celsius (J/g·K or J/g·°C).

51
Q

What is heat change and how do you calculate it?

A

Heat change refers to the amount of heat released or absorbed during a chemical reaction. It is calculated using the formula Q = mass x specific heat x temperature change, where Q is the heat change, mass is the mass of the substance, specific heat is the heat needed to raise the temperature of 1 gram of a substance by 1 degree Kelvin or Celsius, and temperature change is the difference in temperature before and after the reaction.

52
Q

What is a cooling curve?

A

A cooling curve is a graphical representation of the temperature change of a substance over time as it cools down after a reaction or process. It is used to account for heat loss during the reaction and to determine the final temperature of the substance.

53
Q

What is an approximation?

A

An approximation is an estimation or a simplified representation of a value or a concept. In the context of measuring heat changes in experiments, there are several approximations made, such as assuming the density of the solution is similar to water and that the specific heat of the solution is the same as water.

54
Q

How can heat loss be reduced in experiments involving heat changes in solutions?

A

Heat loss can be reduced by using a polystyrene cup to insulate the reaction mixture and a polystyrene lid with a thermometer hole to control heat loss from the liquid’s surface.

55
Q

What equation is needed to calculate the enthalpy change?

A

Q = m c ΔT

56
Q

How is the equilibrium constant Kc calculated?

A

By dividing the concentration of products by the concentration of reactants, with the concentration of each substance raised to a power equal to the number of moles

57
Q

How can the enthalpy change per mole be calculated?

A

The enthalpy change per mole can be calculated by scaling up the heat change in the reaction.

58
Q

Is combustion an exothermic or endothermic reaction?

A

Combustion is an exothermic reaction.

59
Q

What assumptions are made when calculating the heat change in a solution?

A

When calculating the heat change in a solution, it is assumed that the volume of the solution is similar to water and that the specific heat of the solution is the same as water.

60
Q

Why is the accuracy of the thermometer important in experiments involving small temperature changes?

A

The accuracy of the thermometer is important in minimising errors due to small temperature changes.

61
Q

How can you determine the units of Kc for a specific reaction?

A

By putting the units of the substances into the Kc expression and cancelling out some units to give the overall units for Kc

62
Q

What is the purpose of the equilibrium constant, Kc, in Chemistry?

A

The equilibrium constant, Kc, is a concept used in Chemistry to determine the position of equilibrium for a reaction at a specific temperature.

63
Q

What are oxidising agents?

A

Oxidising agents are substances that accept electrons from another substance during a redox reaction. They are electron acceptors and cause the oxidation (loss of electrons) of another substance while undergoing reduction (gain of electrons) themselves.

64
Q

What is oxidation?

A

Oxidation is a chemical process that involves the loss of electrons by a substance. It often occurs when a substance reacts with oxygen or when it loses hydrogen atoms.

65
Q

What is a half equation?

A

A half-equation is a chemical equation that represents either the oxidation or reduction half of a redox reaction. It shows the transfer of electrons between reactants and products.

66
Q

What is electron transfer?

A

Electron transfer refers to the movement of electrons from one substance to another during a chemical reaction. In the context of oxidation and reduction, electron transfer is the basis for the exchange of electrons between oxidising and reducing agents.

67
Q

What is a redox reaction?

A

A redox reaction, also known as an oxidation-reduction reaction, is a chemical reaction in which both oxidation and reduction occur simultaneously. In these reactions, one substance is oxidised (loses electrons) while another substance is reduced (gains electrons).

68
Q

What is an oxidation number?

A

Oxidation number, also known as oxidation state, is a number assigned to an atom in a compound or ion to indicate the distribution of electrons. It represents the hypothetical charge that an atom would have if all its bonds were 100% ionic.

69
Q

What is reduction?

A

Reduction is a chemical process that involves the gain of electrons by a substance. It often occurs when a substance reacts with hydrogen or when it gains oxygen atoms.

70
Q

What is a reducing agent?

A

A reducing agent, also known as a reductant, is a substance that donates electrons to another substance during a redox reaction. It causes the reduction (gain of electrons) of another substance while undergoing oxidation (loss of electrons) itself.

71
Q

What is the significance of specific elements in common compounds?

A

Specific elements maintain consistent oxidation numbers in common compounds.

72
Q

What are the guidelines for determining oxidation numbers?

A

Elements in their pure form have an oxidation number of zero. The sum of oxidation numbers in a compound is zero.

73
Q

What is the term used to describe a reaction where both oxidation and reduction occur simultaneously?

A

A redox reaction.

74
Q

In a redox reaction, what happens to the substances involved?

A

In a redox reaction, the substance that gains electrons is reduced, while the substance that loses electrons is oxidized.

75
Q

What is the difference between oxidation and reduction?

A

Oxidation involves gaining oxygen, while reduction involves losing oxygen.

76
Q

What is done when the substance undergoing oxidation or reduction has changing levels of oxygen?

A

When the substance undergoing oxidation or reduction has changing levels of oxygen, H+ ions and H2O are added to balance the half-equations.

77
Q

How are redox equations balanced?

A

To balance redox equations, half-equations are written for the oxidation and reduction processes.

78
Q

What is the main concept behind oxidation, reduction, and redox reactions?

A

The main concept behind oxidation, reduction, and redox reactions is the transfer of electrons between substances.

79
Q

What is the role of the oxidizing agent and the reducing agent in a redox reaction?

A

The oxidizing agent is the electron acceptor, while the reducing agent is the electron donor.

80
Q
A

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