F325 past papers Flashcards
What reactions are exothermic?
Bond forming
Why is the enthalpy change of hydration of magnesium ions more exothermic than that of calcium ions?
Mg ion is smaller.
Mg2+ has stronger bonding to H2O
Reaction of Acid and Hydroxides.
CH3COOH + Calcium hydroxide
2CH3COOH + Ca(OH)2 —> (CH3COO-)2Ca+ + 2H2O
What is the relationship between pKa and Ka?
pKa = -logKa
Ka=10^-pKa
What are properties of metal ions?
They are catalysts, they are coloured.
How do you write the concentration of a ligand?
Double bracket that baby [ [] ]
Why is CO bad in the blood?
Complex with CO is stronger than with O2, less O2 taken up by haemoglobin.
The Coordinate bond with CO is strong.
What is percentage molar dissociation?
When ka = a/b
a/b x 100
How do you prepare a buffer?
excess of acid, some remains.
Why do feasible reactions not always take place?
The conditions aren’t standard.
Slow rate.
What are advantages of fuel cells over fossil fuels in vehicles?
Less greenhouse gases produced.
Greater efficiency.
When you work out the min temperature what is the units of T?
i.e. 0=178-(0.165 x T)
Kelvin
In endothermic reactions how does Kw change?
Increases with temperature.
Suggest reasons for differences between enthalpy changes of solution of KF and RbF.
KF -15
RbF -24
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.
How can you measure enthalpy change of neutralisation?
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
How do you work out delta Hneutralisation?
Q/moles of H2O
What is the overall equation for a hydrogen fuel cell?
2H2 + O2 —> 2H2O
What are the differences between a fuel cell and regular electrochemical cell?
A fuel cell converts energy from reaction of a fuel with oxygen into electrical energy.
How can hydrogen be stored for fuel in cars?
Under pressure as a liquid.
Adsorbed on sold.
Absorbed within solid.
Why is hydrogen fuel not practical?
Energy is needed to make the fuel cell/hydrogen.
What values do you use to work out the rate constant?
The initial rates.
Compare the lattice enthalpy of magnesium sulphide and sodium oxide.
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.
Why can’t you determine the lattice enthalpy for CO3 2-?
It contains more than one element.
Learn diagrams for enthalpy change of solution.
Yeah yeah do it man
What do you remember when drawing ligand complexes?
Ie CoCl4
Dat charge yo
2-
How do you draw the stereoisomer of a complex ion with 6 Ligands?
Cis has two next to each other at 90*
Trans has them opposite at 180*
How does a buffer react to an addition of an acid?
A- reacts with H+ to form the HA.
Equilibrium shifts to the left.
Why may both cell potentials change slowly?
There are not standard concentrations.
Changes in Kc
Go for it man
Half equations and predicting?
Not a clue
