AQA - Unit 5 - Energetics, Redox and Inorganic Chemistry

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Reply 1620

lou12

Original post by soutioirsim

I swear we didn't have to write an equation for that, just describe the interactions.

yeah, thats what i thought too! i didn't see anything about an equation :confused:

Reply 1621

Zakir

Original post by Betsss

-38 i think

can you show how you worked it out, im not sure....

did you multiply the N-H bond by 6? because theres three of them but two moles of NH3?

Reply 1622

spocckka

Original post by A level Az

Why would you get the mark for doing it wrong/writing the full equation? The question clearly asked for the ionic equations, and to be honest if you knew the full equations it was really easy to work out.

****

Reply 1623

Zakir

Original post by spocckka

****

what question is this?

Reply 1624

A level Az

Original post by Betsss

hehe what were the ionic equations? :tongue:

2Al^3+ + 6Cl^- -----> Al2Cl3

2Al^3+ + 8OH^- ---------> 2Al(OH)4^-

Something like that.

Reply 1625

Betsss

Original post by Zakir

can you show how you worked it out, im not sure....

did you multiply the N-H bond by 6? because theres three of them but two moles of NH3?

I rewrote the equation as:
1/2N2 + 1.5H2 -> NH3

reactants: 0.5 x N2 bond (0.5 x 944) + 1.5 x H2 bond (1.5 x 436) = 1126
products: 3x NH bond = 3x388 = 1164
1126-1164 = -38 Kjmol-1

Reply 1626

spocckka

Original post by Zakir

can you show how you worked it out, im not sure....

did you multiply the N-H bond by 6? because theres three of them but two moles of NH3?

It asked for the enthalpy of formation for one mole of NH3, so you had to divide the equation by two.

Reply 1627

Betsss

Original post by A level Az

2Al^3+ + 6Cl^- -----> Al2Cl3

2Al^3+ + 8OH^- ---------> 2Al(OH)4^-

Something like that.

yeah, i got that too, apart from AlCl3 (as Cl has a 1- charge)
and divided the 2nd equation by 2, as its the simplified ratio

Reply 1628

spocckka

It wanted ionic equation of the reactions of Al2O3 and HCl, and the same for Al2O3 and NaOH. So instead of Al2O3 + HCl... blah blah, it was Al^3+ + 3Cl-....

I'm so stupid, I even considered doing that.

Reply 1629

Betsss

Original post by spocckka

It asked for the enthalpy of formation for one mole of NH3, so you had to divide the equation by two.

yeah, or alternatively, divide the overall answer by 2

Reply 1630

Zakir

Original post by A level Az

2Al^3+ + 6Cl^- -----> Al2Cl3

2Al^3+ + 8OH^- ---------> 2Al(OH)4^-

Something like that.

what if we put..

Al2O3 + 6HCL ----> 2AlCl3

and

Al2O3 + 2NaOH + 3H2O ----> 2NaAl(OH)4...

:s

Reply 1631

Zakir

Original post by spocckka

It asked for the enthalpy of formation for one mole of NH3, so you had to divide the equation by two.

was that for the first part of the question as well?

i only did that for the 4th part...

Reply 1632

A level Az

Original post by Zakir

what if we put..

Al2O3 + 6HCL ----> 2AlCl3

and

Al2O3 + 2NaOH + 3H2O ----> 2NaAl(OH)4...

:s

It asked specifically for the ionic equations, so I wouldn't expect them to give any marks for that. Sorry :frown:

Reply 1633

Zakir

Original post by A level Az

It asked specifically for the ionic equations, so I wouldn't expect them to give any marks for that. Sorry :frown:

hmm...ok thanks

Reply 1634

MrLukee

Original post by A level Az

It asked specifically for the ionic equations, so I wouldn't expect them to give any marks for that. Sorry :frown:

DAAYUM.. Didn't even notice thats what they asked for.. two marks down (N)

Reply 1635

Betsss

What did people get for the value of Delta G then?

Reply 1636

A level Az

Original post by MrLukee

DAAYUM.. Didn't even notice thats what they asked for.. two marks down (N)

Yeah I actually began writing down the full equations first before I saw the word "ionic" :tongue:

Reply 1637

Zakir

does anyone know the UMS marks for EACH module (i.e. empa's and exam)...at AS and A2..

just trying to work out what grade i might be expecting...

thanks!

Reply 1638

MrLukee

Original post by soutioirsim

What did people put for the "How do the fluoride ions interact with the water?" Or something a long the lines.

I put that the fluoride ions act as a lewis base :s