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Chemistry - norm > 4 - Physical Chemistry > Flashcards

4 - Physical Chemistry Flashcards

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1
Q

What is the pH of the strongest acid?

A

pH0 (e.g. a car battery or stomach acid)

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2
Q

What is the pH of the strongest alkali?

A

pH14 (e.g. caustic soda)

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3
Q

What is the pH of neutral?

A

pH7 (e.g. pure water)

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4
Q

What is the universal indicator colour for an acid?

A

Red

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5
Q

What is the universal indicator colour for an alkali?

A

Purple

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6
Q

What is the universal indicator colour for neutral?

A

Green

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7
Q

What colour is litmus paper in acidic solutions?

A

Red

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8
Q

What colour is litmus paper in alkaline solutions?

A

Blue

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9
Q

What colour is litmus paper in neutral solutions?

A

Purple

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10
Q

What colour is phenolphthalein in acidic solutions?

A

Colourless

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11
Q

What colour is phenolphthalein in alkaline solutions?

A

Pink

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12
Q

What colour is methyl orange in acidic solutions?

A

Red

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13
Q

What colour is methyl orange in alkaline solutions?

A

Yellow

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14
Q

What is an acid?

A

A source of H+ ions

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15
Q

What is an alkali?

A

A source of OH- ions

- Can be used as a soluble base

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16
Q

What is a base?

A

A substance that can neutralise an acid
Acid + base –> salt + water
H+ + OH- –> H2O

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17
Q

What does an acid + metal oxide make?

A

Acid + metal oxide –> salt + water

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18
Q

What does an acid + metal carbonate make?

A

Acid + metal carbonate –> salt + water + carbon dioxide

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19
Q

Sodium salts

A

Soluble

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20
Q

Potassium salts

A

Soluble

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21
Q

Ammonium salts

A

Soluble

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22
Q

Nitrates

A

Soluble

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23
Q

Most chlorides

A

Soluble

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24
Q

Silver chloride

A

Insoluble

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25
Q

Most sulphates

A

Soluble

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26
Q

Barium sulphate

A

Insoluble

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27
Q

Calcium sulphate

A

Insoluble

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28
Q

Most carbonates

A

Insoluble

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29
Q

Sodium carbonate

A

Soluble

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30
Q

Potassium carbonate

A

Soluble

31
Q

Ammonium carbonate

A

Soluble

32
Q

How can you make soluble salts using acids and insoluble bases?

A
  • Add the metal oxide, carbonate or hydroxide to the acid
  • The acid has been neutralised when the excess solid sinks to the bottom of the flask
  • Filter out the excess base
  • Evaporate water off for pure solid cystals
33
Q

How can you make soluble salts using acids and insoluble bases?

A
  • Add the metal oxide, carbonate or hydroxide to the acid
  • The acid has been neutralised when the excess solid sinks to the bottom of the flask
  • Filter out the excess base
  • Evaporate water off for pure solid crystals
34
Q

How can you make soluble salts using an alkali?

A
  • You have to add just the right amount to neutralise the acid
  • Use an indicator to show when it is finished
  • The best way is to use titrations
  • Repeat without an indicator so the salt isn’t contaminated
35
Q

How can you make insoluble salts?

A
  • Precipitation reactions
  • Pick two solutions with the ions needed
  • mix together
36
Q

What is the equation to work out the moles of a concentration?

A

moles = concentration x volume

37
Q

When are titrations used?

A

To find out the exact concentration of how much acid is needed to neutralise a quantity of alkali (or vice versa)

38
Q

Describe how to do a titration

A
  • Using a pipette and pipette filler add some alkali (about 25cm3) to a conical flask with some drops of indicator
  • Fill a burette with the acid at eye level
  • Using the burette, add the acid to the alkali slowly whilst stirring and go very slowly towards the end point
  • The indicator changes colour when all the alkali has been neutralised
  • Record the volume of acid to neutralise the alkali
  • Repeat
39
Q

What does a pipette do?

A

Measures only one volume of solution

40
Q

What does a burette do?

A

Measures different volumes and let you add the solution drop by drop

41
Q

What is an example of a slow rate of reaction?

A

The rusting of iron

42
Q

What is an example of a moderate rate of reaction?

A

A metal reacting with an acid to form bubbles

43
Q

What is an example of a fast rate of reaction?

A

An explosion

44
Q

What factors effect the rate of reaction?

A
  • Temperature
  • Concentration (or pressure for gases)
  • Catalyst
  • Size of particles (or surface area)
45
Q

What is the equation for rate of reaction?

A

Rate of reaction = amount of reactant used or amount of product formed / time

46
Q

What is the equation for rate of reaction?

A

Rate of reaction = amount of reactant used or amount of product formed / time

47
Q

How can you measure the rate of reaction with precipitation?

A
  • the product must form a cloudy precipitate
  • Observe a marker through the solution and measure how long it takes to disappear
  • The quicker it disappears the quicker the reaction
  • Use a timer
  • Not very accurate as there are different views on when the marker has disappeared
48
Q

How can you measure the rate of reaction with the change in mass?

A
  • On a mass balance
  • Time how long it takes for the mass to stop dropping
  • When it stops changing the reaction has stopped
  • The most accurate method as the mass balance is very accurate
49
Q

How can you measure the rate of reaction with the volume of gas given off?

A
  • Involves a gas syringe
  • The more gas given off in a shorter time period the faster the reaction
  • Gas syringes are very accurate so very accurate method
50
Q

Describe an experiment for volume of gas

A
  • Hydrochloric acid and marble chips
  • Measure the volume of gas with a gas syringe
  • Repeat with the marble chips more crunched up
  • The more powdered the marble chips are the faster the reaction as there is a larger surface area
51
Q

Describe an experiment for the loss in mass

A
  • Magnesium metal in dilute HCl
  • Gives off hydrogen gas
  • Use a mass balance to measure the amount of mass lost
  • Use a timer
52
Q

Describe an experiment for a cloudy precipitate

A
  • Sodium thiosulphate and HCl produce a cloudy yellow precipitate of sulphur
  • Time how long it takes for the cross to disappear
  • Can be heated in a water bath to show the effects of temperature increase
53
Q

Describe an experiment for volume of gas through decomposition

A
  • The decomposition of hydrogen peroxide (H2O2)
  • Catalyst of manganese(IV) oxide
  • Other catalysts can be potato peel or blood
  • Oxygen gas is given off which is measure in a gas syringe
  • Repeat using stronger catalysts
54
Q

Describe an experiment for volume of gas through decomposition

A
  • The decomposition of hydrogen peroxide (H2O2)
  • Catalyst of manganese(IV) oxide
  • Other catalysts can be potato peel or blood
  • Oxygen gas is given off which is measure in a gas syringe
  • Repeat using stronger catalysts
55
Q

How does temperature increase the rate of reaction?

A
  • Particles have more energy
  • Move around more
  • Collide more frequently and with more force
56
Q

How does the concentration (or pressure) increase the rate of reaction?

A
  • More concentrated means more particles knocking about
  • More collisions
  • In a gas they are more squashed together so collide more frequently
57
Q

How does a larger surface area increase the rate of reaction?

A
  • Larger surface area means more area to ‘work on’

- More collisions more often

58
Q

How does a catalyst increase the rate of reaction?

A
  • Works by giving the particles an easier pathway to each other
  • Lowers the activation energy so the particles have more energy to react
59
Q

What is the activation energy?

A

The initial energy needed to break bongs

60
Q

What is an exothermic reaction?

A
  • Energy is given out to the surroundings (normally as heat)
  • Show by a rise in temperature
  • Bond forming is exothermic
  • On a graph the products is below the reactants
61
Q

What is an endothermic reaction?

A
  • Energy is taken from the surroundings (normally as heat)
  • Shown by a drop in temperature
  • Bond breaking is endothermic
  • On a graph the products are above the reactants
62
Q

What is the enthalpy change?

A

The overall energy change in the reaction

  • Positive number = endothermic
  • Negative number = exothermic
63
Q

What does an energy level diagram look like with a catalyst?

A

The line will be lower than the line without a catalyst

64
Q

What is the equation for enthalpy change?

A

Enthalpy change = total energy absorbed in breaking bongs - total energy released in making bonds

65
Q

What is the bond energy?

A

The total amount of energy in a bond

- Changes with every compound

66
Q

How can you find enthalpy changes using calorimetry?

A
  • Used for dissolving, displacement or neutralisation reactions
  • Mix the reactants in a polystyrene cup
  • Reduce heat loss by putting it in a beaker of cotton wool to provide insulation
  • To reduce evaporation put a lid on the cup
67
Q

How can you find enthalpy changes using calorimetry?

A
  • Used for dissolving, displacement or neutralisation reactions
  • Mix the reactants in a polystyrene cup
  • Reduce heat loss by putting it in a beaker of cotton wool to provide insulation
  • To reduce evaporation put a lid on the cup
  • Take the temperature every 30s until it reaches its peak
68
Q

How can you find enthalpy changes using calorimetry (combustion)?

A
  • Heat 50cm3 of water in a copper container (conductor of heat) and record initial temperature
  • Use a screen to act as a draught excluder (and stay away from an open window)
  • Weigh the spirit burner and lid
  • Stir constantly and check temperature until it reaches 50*C
  • Put out the flame and measure finial temperature of water
  • Weigh the spirit burner and lid again
  • Calculate the enthalpy change
69
Q

How can you calculate the molar enthalpy change?

A
  • Calculate the energy transferred
  • Work out how many moles were produced (m = m / Mr)
  • Divide the energy produced by the moles
70
Q

How can you calculate the energy transferred?

A
  • Work out the amount of reactant burnt (using measurements taken during the experiment)
  • Work out the temperature before and after heating
  • 4.2 x amount of reactant x temperature difference
  • Answer in joules
71
Q

Give an example of a reversible reaction

A
  • Thermal decomposition of ammonium chloride (NH4Cl)
  • White solid breaks into ammonia and hydrogen gases
  • Cooling returns it to ammonium chloride
72
Q

What is a dynamic equilibrium?

A
  • When the relative quantities of reactants and products will reach a certain balance and stay there
  • The forward and reverse reactions cancel each other out
  • Taking place at exactly the same rate
73
Q

How can changing the temperature give you more product? (reversible reactions)

A
  • the endothermic will use up more heat

- The exothermic reaction will give out more heat

74
Q

How can changing the pressure give you more product? (reversible reactions)?

A
  • If raised it will encourage the reaction with fewer molecules of gas (the endothermic reaction)
  • If lowered it will encourage the reaction with more molecules of gas (exothermic)

Chemistry - norm (6 decks)

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