AQA AS Chemistry: 8th June

no you cant u fool, i just hope your in as level and can retake next year! you will realise then how silly u were to do that!

Reply 42

thefish_uk

Oughta say it's only infinite because it can be fermented from renewable sugar.

Indeed.

Q: Give all the equations involved in the extraction of iron by carbon reduction in the blast furnace, including the removal of impurities.

Reply 43

C + O2 --> CO2
C + CO2 --> 2CO
Fe2O3 + 3CO --> 2Fe + 3CO2
2Fe2O3 + 3C --> 4Fe + 3CO2
CaCO3 --> CaO + CO2
CaO + SiO2 --> CaSiO3
slag

Mg + S -->MgS
2C + O2 -->2CO
P4 + 5O2 --> P4O10

define the standard enthalpy of formation and the mean bond enthalpy

Reply 44

Standard enthalpy of formation: The enthalpy change when one mole of a substance is formed from its elements in their standard states.

Mean bond enthalpy: The amount of energy required to break a particular bond averaged out over a range of similar compounds.

Erm ... What is Le Chatelier's Principle? What are the (approx) conditions for the Haber process and why?

Reply 45

wednesburywench

C + O2 --> CO2
C + CO2 --> 2CO
Fe2O3 + 3CO --> 2Fe + 3CO2
2Fe2O3 + 3C --> 4Fe + 3CO2
CaCO3 --> CaO + CO2
CaO + SiO2 --> CaSiO3
slag

Mg + S -->MgS
2C + O2 -->2CO
P4 + 5O2 --> P4O10

define the standard enthalpy of formation and the mean bond enthalpy

Btw, in my notes I haven't got 2Fe2O3 + 3C --> 4Fe + 3CO2, I've got Fe2O3 + 3C --> 2Fe + 3CO instead.

Reply 46

you have to put for the formation all elements in standard states, and UNDER STANDARD CONDITIONS for the full marks if it says standard.

Le chateliers=- A system will respond to a change in condition by shifting the equilibrium to oppose the change. Lowish temperature, highish pressure, (both are compromises between rate and costs) 2000kpa and 700ishK

Reply 47

sorry your equations right just checked! oh god id learned a wrong one by some reason!!!

Reply 48

Scottus_Mus

1

Kiesha

Btw, in my notes I haven't got 2Fe2O3 + 3C --> 4Fe + 3CO2, I've got Fe2O3 + 3C --> 2Fe + 3CO instead.

Both are acceptalbe

Reply 49

Define elecronegativity.

Reply 50

The ability of an atom to withdraw electron density from a covalent bond.

Define first ionisation energy. Give the equations for the first 3 ionisation energies of Mg.

Reply 51

daaavo

heeeeeeeeeeeeeeeelp...... what is the relative mass of an electron?????

Reply 52

The enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous unipositive cations.
Mg(g) -> Mg+(g) + e
Mg+(g) -> Mg2+ + e
Mg2+(g) -> Mg3+ + e

Describe what observations you would make when Sodium Iodide is added to Sulphuric Acid.

Reply 53

what is the relative mass of an electron?????

1/1837 there are lots of variations on that number... thats just the one ive learnt

Reply 54

daaavo

thanx soooooo much... gud luck!!!

Reply 55

Joseppi

wednesburywench

slag

hehe

Reply 56

franks

The enthalpy change when one mole of electrons is removed from one mole of gaseous atoms to form one mole of gaseous unipositive cations.
Mg(g) -> Mg+(g) + e
Mg+(g) -> Mg2+ + e
Mg2+(g) -> Mg3+ + e

Describe what observations you would make when Sodium Iodide is added to Sulphuric Acid.

HI - misty fumes
H2S - colourless, bad egg smelling gas
I2 - purple vapour/black solid

(? not too sure)

Describe, briefly, how a mass spectrometre works.

Reply 57