AQA CHEM5 A2 Chemistry - 19th June 2013

we do not need to know any knowledge of batteries/cells other than the hydrogen oxygen fuel cell. We also need to be able to talk about the relative advantages and disadvantages of the hydrogen-oxygen fuel cell.

Does anyone know the definition for 'enthalpy of atomisation of a compound'

The question is actually:
"Calculate the temperature ABOVE WHICH the reaction between hydrogen and oxygen to form gaseous water is not feasible."

we do not need to know any knowledge of batteries/cells other than the hydrogen oxygen fuel cell. We also need to be able to talk about the relative advantages and disadvantages of the hydrogen-oxygen fuel cell.

Does anyone know the definition for 'enthalpy of atomisation of a compound'

The standard enthalpy change which accompanies the formation of 1 mole of gaseous atoms from its element in its standard state and under standard conditions

Yes

What is there to know about the hydrogen fuel cell?! Also, how do I know when to multiply the enthalpy of atomisation for a diatomic molecule, and when not to?

yes - that is the definition of the standard enthalpy of atomisation of an element, but not of a compound. I was wondering if anyone has any textbook definitions (since its on the spec. but not in the textbook)

It could also be H₂O₂ + 2H⁺ + 2e^- $\rightarrow$ 2H₂O, just depends what the question specifies

WHAT COLOUR WILL DEFINATELY GET ME MARKS FOR HEXAAQUACHROMIUM??? green solution or ruby

WHAT COLOUR WILL DEFINATELY GET ME MARKS FOR HEXAAQUACHROMIUM??? green solution or ruby

The Enthalpy of atomisation of a compound is the enthalpy change when 1 mole of a compound in its standard state is converted to gaseous atoms, e.g NaCl(s) ----> Na(g)+Cl(g)

Can someone please help me with January 2011 the last question. I can do the calculation but I do not know how to balance the equation...It would be a big help.

I'm being really dumb, but its the wording of the question that confused lol Can't get my head round it lol

both but prefered purple i think ;p i still say green though ;p cuz all the Cr3+ ions are green(apart from [Cr(NH3)6]3+ which is purple)

hmm good question - I think it depends on the phrasing of the question. Firstly, they'll always accept either..

but if it says 'what is the colour of the hexaaquachromium(III) ion / [Cr(H2O)6], then I'd put ruby.

If the question asked for the colour of chromium(III) ions in aqueous solution, then I'd say green.