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Chemistry > Section 4: Physical Chemistry > Flashcards

Section 4: Physical Chemistry Flashcards

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1
Q

what colour is litmus indicator in the presence of acidic, neutral and alkaline solutions?

A

acidic: red
neutral: purple
alkaline: blue

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2
Q

what colour is methyl orange indicator in the presence of acidic, neutral and alkaline solutions?

A

acidic: red
neutral: orange
alkaline: yellow

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3
Q

what colour is phenolphtalein indicator in the presence of acidic, neutral and alkaline solutions?

A

acidic: colourless
neutral: colourless
alkaline: pink

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4
Q

what are acids?

A

sources of hydrogen ions (H+)

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5
Q

what are alkalis?

A

sources of hydroxide ions (OH-)

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6
Q

what are the products of the reaction of acids and metals?

A

salt + hydrogen

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7
Q

what are the products of the reaction of acids and metal oxides?

A

salt + water

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8
Q

what are the products of the reaction of acids and metal carbonates?

A

salt + water + carbon dioxide

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9
Q

what are the rules for predicting the solubility of salts?

A

1) sodium, potassium and ammonium salts are soluble
2) all nitrates are soluble
3) chlorides are soluble except silver chloride
4) sulphates are soluble except those of barium and calcium
5) carbonates are insoluble except those of sodium, potassium and ammonium

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10
Q

how do you prepare soluble salts from acids?

A

react an acid with an excess of metal/ insoluble base

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11
Q

how do you prepare copper sulphate?

A

1) add excess copper oxide to sulfuric acid, heating and stirring to speed up the reaction
2) solution turns blue as reaction occurs
3) filter solution to remove excess copper oxide
4) evaporate the water so that crystals of copper sulphate are left behind

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12
Q

how do you prepare insoluble salts?

A

1) react two soluble salts to form a precipitate
2) filter the solution to get the precipitate
3) wash the salt with pure water to remove traces of the other solution and leave to dry

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13
Q

give an example of an insoluble salt preparation

A

insoluble silver chloride formed by this reaction:

silver nitrate + sodium chloride –> silver chloride + sodium nitrate

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14
Q

how do you carry out acid-alkali titrations?

A

1) use burette to add acid to alkali drop by drop, swirling the solution periodically
2) stop adding acid once there is a change in the colour of the indicator
3) take initial and final readings of the acid and subtract to calculate the volume added
4) repeat until obtain concordent results

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15
Q

what is the purpose of titrations?

A

1) identify the concentration of acids/alkalis

2) make salts with no leftover acid/alkali

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16
Q

what does ΔH represent?

A

molar enthalpy change (energy transferred from bonds to heat)

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17
Q

how do you calculate heat energy changes in simple calorimetry experiments?

A 
Energy = m x c x ΔT
m= mass of water
c= SHC of water (4.2J kg °C)
T= temperature change of water
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18
Q

for exothermic reactions on a diagram are the products of the reaction below or above the reactants?

A

Below

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19
Q

for endothermic reactions on a diagram are the products of the reaction below or above the reactants?

A

Above

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20
Q

is ΔH a negative or positive value for exothermic reactions?

A

negative

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21
Q

is ΔH a negative or positive value for endothermic reactions?

A

positive

22
Q

is the breaking of bonds endothermic or exothermic?

A

endothermic

23
Q

is the making of bonds endothermic or exothermic?

A

exothermic

24
Q

how does an increase in surface area increase the rate of reaction?

A

1) more sites for the reaction to take place

2) more frequent collisions

25
Q

how does an increase in concentration/pressure increase the rate of reaction?

A

1) more particles in a given volume

2) more frequent collisions

26
Q

how does an increase in temperature increase the rate of reaction?

A

Firstly:
1) particles have more kinetic energy
2) more frequent collisions
Secondly:
1) particles have more energy
2) higher proportion of particles have energy equal to or above the activation energy
3) higher proportion of successful collisions

27
Q

what is the activation energy?

A

the minimum energy required for a reaction to start

28
Q

how do catalysts speed up reactions?

A

they provide an alternative pathway with a lower activation energy

29
Q

what does ⇌ mean?

A

the reaction is in equilibrium (reversible)

30
Q

what is the affect of increasing the temperature on the equilibrium reaction of ammonia chloride to hydrogen chloride and ammonia?

A

shift towards the endothermic reaction (more hydrogen chloride and ammonia)

31
Q

what kind of reaction is the dehydration of hydrated copper sulphate?

A

reversible reaction

32
Q

what is true of something in dynamic equilibrium?

A

1) the rate of the forward reaction is equal to the rate of the backward reaction
2) the concentrations of the products and reactions are constant (but no necessarily equal)
3) forwards and backwards reactions occur at the same time

33
Q

what is the affect of increasing the temperature on the equilibrium position in reversible reactions?

A

shifts in the endothermic direction

34
Q

what is the affect of increasing the pressure on the equilibrium position in reversible reactions?

A

shifts to the side with the fewest gaseous moles

35
Q

What name is given to a reaction that involves both reduction and oxidation?

A

Redox

36
Q

What kind of reaction is metal reacting with acid to form a salt?

A

Neutralisation

37
Q

Why is universal indicator not a good choice for titration experiments?

A

colour change is gradual/not defined

38
Q

Explain why increases in pressure increases the rate of reaction in terms of particle collision theory

A

1) particles closer together

2) particles collide more frequently

39
Q

Explain in terms of making and breaking bonds why reactions are exothermic

A

1) breaking bonds is endothermic
2) making bonds is exothermic
3) more heat energy given out than taken in

40
Q

How could a dry gas be collected?

A

Using a gas syringe

41
Q

Describe two observations made when magnesium burns in air

A

1) white solid produced

2) bright white flame

42
Q

In the excess metal/salt method why is excess added?

A

To neutralise the acid

43
Q

How do you calculate molar enthalpy change from heat energy change?

A 
ΔH = q ÷ m
q = heat energy
m = moles
44
Q

How do you use average bond energies to calculate molar enthalpy change?

A

1) draw out molecules showing bonds
2) calculate reactants energy
3) calculate products energy
4) energy change = bonds broken - bonds made

45
Q

Why are acids heated before the base or metal is added?

A

To increase the rate of reaction

46
Q

How do you know when a salt or base is in excess?

A

It stops disappearing and forms as a solid at the bottom of the beaker

47
Q

How do you know when the crystallisation point is reached?

A

A drop of solution forms crystals when removed and cooled

48
Q

Why are noble gases inert?

A

1) atoms do not readily lose or gain electrons

2) as contains 8 electrons in outer shell

49
Q

explain why potassium is more reactive than sodium

A

1) outer electron lost in K further from the nucleus

2) less attracted by nucleus

50
Q

suggest why copper strips would dry more quickly when washed with ethanol rather than water

A

ethanol is more volatile

Chemistry (5 decks)

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