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A2 Chemistry > F325 past papers > Flashcards

F325 past papers Flashcards

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1
Q

What reactions are exothermic?

A

Bond forming

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2
Q

Why is the enthalpy change of hydration of magnesium ions more exothermic than that of calcium ions?

A

Mg ion is smaller.

Mg2+ has stronger bonding to H2O

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3
Q

Reaction of Acid and Hydroxides.

CH3COOH + Calcium hydroxide

A

2CH3COOH + Ca(OH)2 —> (CH3COO-)2Ca+ + 2H2O

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4
Q

What is the relationship between pKa and Ka?

A

pKa = -logKa

Ka=10^-pKa

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5
Q

What are properties of metal ions?

A

They are catalysts, they are coloured.

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6
Q

How do you write the concentration of a ligand?

A

Double bracket that baby [ [] ]

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7
Q

Why is CO bad in the blood?

A

Complex with CO is stronger than with O2, less O2 taken up by haemoglobin.
The Coordinate bond with CO is strong.

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8
Q

What is percentage molar dissociation?

A

When ka = a/b

a/b x 100

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9
Q

How do you prepare a buffer?

A

excess of acid, some remains.

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10
Q

Why do feasible reactions not always take place?

A

The conditions aren’t standard.

Slow rate.

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11
Q

What are advantages of fuel cells over fossil fuels in vehicles?

A

Less greenhouse gases produced.

Greater efficiency.

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12
Q

When you work out the min temperature what is the units of T?
i.e. 0=178-(0.165 x T)

A

Kelvin

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13
Q

In endothermic reactions how does Kw change?

A

Increases with temperature.

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14
Q

Suggest reasons for differences between enthalpy changes of solution of KF and RbF.
KF -15
RbF -24

A

Ionic radius
Potassium ion is smaller

Lattice enthalpy
Lattice enthalpy of KF is more negative than RbF,
or K+ has greater attraction for F–

Hydration of K+ is more negative than Rb+,
or K+ has a greater attraction for H2O

Enthalpy change of solution is affected more by lattice enthalpy than by hydration enthalpy.

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15
Q

How can you measure enthalpy change of neutralisation?

A

Mix and acid and alkali of equal volumes.
Temperature taken at the start and finish.

Energy/Q = mc delta T
m = vol of solution/mass of reactants
c = specific heat capacity of water (4.18)
delta T = temperature change

Energy scaled up to form 1 mol of water.

Enthalpy change of neutralisation = -energy change

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16
Q

How do you work out delta Hneutralisation?

A

Q/moles of H2O

17
Q

What is the overall equation for a hydrogen fuel cell?

A

2H2 + O2 —> 2H2O

18
Q

What are the differences between a fuel cell and regular electrochemical cell?

A

A fuel cell converts energy from reaction of a fuel with oxygen into electrical energy.

19
Q

How can hydrogen be stored for fuel in cars?

A

Under pressure as a liquid.
Adsorbed on sold.
Absorbed within solid.

20
Q

Why is hydrogen fuel not practical?

A

Energy is needed to make the fuel cell/hydrogen.

21
Q

What values do you use to work out the rate constant?

A

The initial rates.

22
Q

Compare the lattice enthalpy of magnesium sulphide and sodium oxide.

A

Mg2+ is smaller and has greater charge density.
Na+ is opposite

S-2 is larger however and O2 is smaller with a higher charge density.

Mg2+ has a stronger attraction and S-2 has a weaker attraction.
Na+ has a weaker but O2- stronger.
Thus hard to compare the two.

23
Q

Why can’t you determine the lattice enthalpy for CO3 2-?

A

It contains more than one element.

24
Q

Learn diagrams for enthalpy change of solution.

A

Yeah yeah do it man

25
Q

What do you remember when drawing ligand complexes?

Ie CoCl4

A

Dat charge yo

2-

26
Q

How do you draw the stereoisomer of a complex ion with 6 Ligands?

A

Cis has two next to each other at 90*

Trans has them opposite at 180*

27
Q

How does a buffer react to an addition of an acid?

A

A- reacts with H+ to form the HA.

Equilibrium shifts to the left.

28
Q

Why may both cell potentials change slowly?

A

There are not standard concentrations.

29
Q

Changes in Kc

A

Go for it man

30
Q

Half equations and predicting?

A

Not a clue

A2 Chemistry (15 decks)

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