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Physical Chemistry Flashcards

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1
Q

Define an Exothermic Reaction:

A
  • Gives out energy to surroundings in form of heat
  • Shown by rise in temperature of surroundings
  • Negative enthalpy change
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2
Q

Define Endothermic Reaction:

A
  • Takes in energy from surroundings in form of heat
  • Shown by fall in temperature of surroundings
  • Positive enthalpy change
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3
Q

What is Enthalpy Change?

A

The overall change in energy in reaction

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4
Q

What is the Reaction Profile of an Exothermic Reaction?

A
  • Products lower energy than reactants

* Difference In height = energy given out in reaction

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5
Q

What is the Activation Energy?

A
  • Minimum amount of energy the reactants need to collide with each other and react
  • Initial rise in energy - energy needed to start reaction
  • Amount of energy particles need to break bonds
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6
Q

What is the Reaction Profile for an Endothermic Reaction?

A
  • Products higher energy than reactants

* Difference In height = energy taken in in reaction

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7
Q

What is Calorimetry?

A
  • Use to find Enthalpy Change

* Measure amount of energy transferred in chemical reaction

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8
Q

How do you measure Energy Transferred in Dissolving, Displacement and Neutralisation Reactions?

A
  • Get temperature of reactions (same temp)
  • Mix then
  • Measure temperature of solution at end
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9
Q

How can you measure the Energy Transferred in Neutralisation Reaction between Hydrochloric Acid (HCl) and Sodium Hydroxide (NaOH)?

A
  • 25cm^3 HCl and NaOH in separate beakers
  • Beakers In water bath at 25 degrees
  • Add HCl, then NaOH to polystyrene cup
  • Take temperature of mixture every 30secs, record highest temperature
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10
Q

How do you do an Combustion Experiment to Calculate Enthalpy Change?

A
  • 50g water in copper can & record temperature
  • Weigh spirit burner & lid
  • Flame to heat water, stir until 50 degrees
  • Method uses metal container (made of copper - conducts heat)
  • Put our flame
  • Weigh spirit burner & lid
  • Calculate enthalpy change
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11
Q

Heat Energy Transferred =

A

Mass if liquid being heated x 4.2 x change in temperature of liquid

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12
Q

What happens during chemical reactions?

A

•Old bones are broken and new bonds are formed

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13
Q

Why is bond formation an exothermic process?

A

Energy is released when you bonds are formed

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14
Q

Why is bond formation an endothermic process?

A

Energy must be supplied to break existing bonds

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15
Q

Enthalpy change =

A

Total energy absorbed to break bonds - Total energy released in making bonds

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16
Q

What is a Rate of a Chemical Reaction?

A

How fast the reactants are changed in products

17
Q

Steeper line =

A

Faster rate of reaction

18
Q

What does the Rate of a Chemical Reaction depend on?

A

•Collision frequency of particles -more collisions = faster reaction •Energy transferred during collision- particles collide with enough energy to be successful

19
Q

What Factors affect the Rate of Reaction?

A
  • Temperature
  • Surface area
  • Catalyst
  • Concentration of solution/pressure of gas
20
Q

What happens if you double Concentration/Pressure/Surface Area to Rate?

A
  • Double number of particles available
  • Frequency of collisions increase
  • Rate increases
21
Q

What happens if you Increase Temperature or have a Catalyst to Rate?

A
  • Increase number of particles with enough energy
  • Increase proportion of collisions which are successful
  • Rate increases
22
Q

What is a Catalyst?

A

Substance which increases rate of reaction, without being chemically changed or used up in the reaction

23
Q

How can you see the Effect of Catalyst using a Reaction Profile?

A

Highest point on curve for reaction with a catalyst than without a catalyst

24
Q

Rate of Reaction =

A

Amount of reactant used or amount of product formed / time

25
Q

How can you use Precipitation to Measure the Rate of a Reaction?

A
  • Mix 2 reactant solutions, put flask over a mark on paper

* The faster the mark disappears = faster rate of reaction

26
Q

How do you Measure Rate of Reaction that Produce a Gas using a Mass Balance?

A
  • Gas released, lost mass measured in balance

* Quicker reading on balance drops = faster rate of reaction

27
Q

How do you Measure how Surface Area affects Rate?

A
  • Conical flask with dilute HCl, marble chips, gas syringe attached
  • measure volume produced by gas syringe, take readings at regular time, record them
  • Plot graph of results
  • Repeat experiment but marble more crunched up
  • Repeat with same mass of powdered chalk
28
Q

Why does Finer Particles mean a Higher Rate?

A
  • Marble has a larger surface area
  • Faster reaction
  • More gas evolved
29
Q

How do you Measure how Concentration affects Rate of Reaction?

A
  • Apparatus using marble chips, HCl, gas syringe attached
  • Measure volume of gas produced in gas syringe
  • Readings at regular time, record
  • Plot graph of results
  • Repeat experiment but different concentration of acid
  • Higher Concentration = faster reaction
30
Q

When Sodium Thiosulfate and Hydrochloric Acid React what do they Form?

A

Yellow Precipitate and Sulfur

31
Q

How can you Measure how Temperature affects the Rate of Reaction?

A
  • Watch a black mark disappear through cloudy sulfur and time how long it takes
  • Repeat at different temperatures and compare
  • Higher temperature = faster rate of reaction
32
Q

What is the Decomposition of Hydrogen Peroxide (H2O2)?

A

2H2O2 - 2H2O + O2

33
Q

How can you Measure how using a Catalyst affects the Rate of Reaction?

A
  • Conical flask with catalyst (MnO2), hydrogen peroxide (H2O2), gas syringe attached
  • Measure volume of gas produced in syringe
  • Record results
  • Repeat experiment but different catalyst (copper oxide)
  • Better catalyst = quicker rate of reaction
34
Q

What is a Reversible Reaction?

A
  • Products of reactants react with each other and convert to original reactant
  • Can go both ways
35
Q

Describe a Reversible Reaction for Ammonium Chloride:

A
  • Ammonium chloride-white solid
  • Heated, breaks down to gases -ammonia & hydrogen chloride (forwards reaction)
  • Cool it, re-form solid (backwards reaction)
36
Q

What does Equilibrium mean?

A

Concentration of reactants and products will reach certain balance and stay there

37
Q

What is Dynamic Equilibrium?

A

•Reactions taking place at exactly same rate in both reactions

38
Q

How does Changing the Temperature get you more Product and Shift Equilibrium to right?

A
  • Increase - endothermic reaction Increase to use up extra heat
  • Decrease - exothermic reaction Increase to give out more heat
39
Q

How does Changing the Pressure get you more Product and Shift Equilibrium to right?

A
  • Increase - encourage reaction which produces fewer gas moles
  • Decrease - encourage reaction which produces more gas moles

Chemistry (10 decks)

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