Some chemistry calculations

[Bugz]

Right - due to the fact my teachers a total spoon & only talks to us about how many holidays he goes on or what have you, i'm a bit stuck on the ol' chemistry calculations.

Would anyone be able to have a go at these two so I can see how my answers shape up to yours?

Rep will be on offer etc.

(a) When iron(III) hydroxide is heated to a high temperature, iron(III) oxide is formed:

2Fe(OH)(small 3) -> Fe(small 2)O(small 3) + 3H(small two)O

Calculate the maximum volume of gaseous water formed at this temperature from 5.35g of iron(III) hydroxide.

(Relative atomic masses: H = 1.0; O = 16; Fe = 56 - 1 mol of a gas occupied 60.0 dm³ under these conditions of temperature & pressure.)

-------

(b) Another oxide of iron consists of 72.4% iron by mass. Calculate the empirical formula of this oxide.


Thanks in advance & if you any of you work for revision guide publishers - tell them to include extension chemistry into their notes!

 

[crispy]

a)
You need to solve how many moles of gas you create first. Tip: Fe2O3 probably doesnt sublimize, so you only have 1½ moles of gas (water) for every mole of Fe(OH)3 you react. Altho they say maximum volume which probably mean you need to take the number of moles (½) of Fe2O3.

When you know how many moles you get as gas you can calculate the volume.

b)
Tip: Iron oxides is iron and oxygen in some form, like FexOy, so the mass of the oxide is x * MFe + y * MO.

So the mass of the oxide m is:

m = x * MFe + y * MO and you know that iron makes up for 72.4% of that mass.

The M's symbolize molar weight of the element.

 

[DocWolfe]

get one of them revision books/guides... they are pretty good and it will explain how to do it instead of you getting the answers off us.

 

[Amildin]

a) 3dm

b) Im not sure, i got them in ratio of 1.293 : 1.725. I assumed the rest of the mass was made up by Oxygen. Too tired to work at it for long, sorry.

 

[Bugz]

a) 3dm

b) Im not sure, i got them in ratio of 1.293 : 1.725. I assumed the rest of the mass was made up by Oxygen. Too tired to work at it for long, sorry.

You sure (a) is 3dm?

Surely if theres more of dilute nitric acid then to neutralise the sodium hydroxide, you'll need a lower conc. than 0.200 mol dm


@Doc - goodluck finding a good revision book for extension gcse science... =/

 

[DocWolfe]

You sure (a) is 3dm?

Surely if theres more of dilute nitric acid then to neutralise the sodium hydroxide, you'll need a lower conc. than 0.200 mol dm


@Doc - goodluck finding a good revision book for extension gcse science... =/

It looks like A-Level stuff to me... get an A-Level book.

 

[Bugz]

It looks like A-Level stuff to me... get an A-Level book.

My exam is thursday so don't really have enough time

& I hope it isn't a-level. I don't even want to do this fuckin exam but alas - I am not the decider.

 

[DocWolfe]

My exam is thursday so don't really have enough time

& I hope it isn't a-level. I don't even want to do this fuckin exam but alas - I am not the decider.

All those titration questions and crap I did at a-level

 

[uron]

this is easy AS level calculations, or harder GCSE...
A) has been explained
B) divide the %age by the RAM of the atom, so is 72.4/56 and 27.6/16, this gives 2 random numbers..you then divide them both by the lowest number, so you get 1 : 1.33
you can get away without using moles on the first one if you know exactly what your doing, but its a bad habit tht i got into, and it doesnt help at a higher level

gimme a shout if u need a hand!

 

[Elkie]

Still wonder to this day how I got all A's in science at GCSE lol... Come back if need help in Media/History/English/Film studies/Theatre Studies . Good luck in your exam though.

 

[Amildin]

this is easy AS level calculations, or harder GCSE...
A) has been explained
B) divide the %age by the RAM of the atom, so is 72.4/56 and 27.6/16, this gives 2 random numbers..you then divide them both by the lowest number, so you get 1 : 1.33
you can get away without using moles on the first one if you know exactly what your doing, but its a bad habit tht i got into, and it doesnt help at a higher level

gimme a shout if u need a hand!

Thats what i got for B but it cant be as that would make the empirical formula FeO. Im too tired for this, g'night

 

[uron]

Thats what i got for B but it cant be as that would make the empirical formula FeO. Im too tired for this, g'night

yea u need to round it up i think, so it would b Fe(3)O(4), which exists.

 

[Lenore]

this makes me soooo happy that ive finished chemistry now as i cant remember a sodding thing. yay for me! silly useless chemistry

 

[Bugz]

Can someone write out the fuckin calculations for working it out please as I'm confused.

 

[Naetha]

Still wonder to this day how I got all A's in science at GCSE lol... Come back if need help in Media/History/English/Film studies/Theatre Studies . Good luck in your exam though.

Same lol only I got an A in chemistry and a C at A-level, and this makes as much sense to me as...well, stuff that doesn't make sense...

I'm good at geology

 

[Nate]

Can someone write out the fuckin calculations for working it out please as I'm confused.

What's with all the hostility? These guys are trying to help you. Calm down dear!

 

[Congax]

What's with all the hostility? These guys are trying to help you. Calm down dear!

He was being fucking hostile nate you ignorant fucking prick

 

[crispy]

Now shut the fuck up both of you or im gonna fucking fuck.. FUCK!!

 

[Congax]

He was being fucking hostile nate you ignorant fucking prick

fuck, that had to be 'wasn't being hostile'

I fucked the fun up

 

[Nate]

Fuck that shit I'm going mother fucking emo fuck on you <cuts> have some blood fuck! <flicks emo hair and puts on chemical romance>

puppy is calling, time for afk!

 

[Bugz]

What's with all the hostility? These guys are trying to help you. Calm down dear!

No hostility.

Just...panic.

 

[Everz]

u on OCR bugz?

 

[Congax]

u on OCR bugz?

He's on XTC

 

[Bugz]

u on OCR bugz?

Edexcel.

*****.

My teacher has not taught us extension chemistry. The whole class has self taught over the last 2-3 days or so.

We're all going to fail.

Woohoo.

Only 3 exams left and something was BOUND to go wrong.

/emo

 

[Lenore]

welcome to the world of a level chemisty!

 

[Bugz]

welcome to the world of a level chemisty!

It's GCSE

Fuck a-level.

 

[Succi]

I can honestly say that (except maybe helping getting into a 6th form) GCSE chemistry extension won't do shit for you


so dont worry

 

[old.windforce]

I can honestly say that MSc chemistry won't do shit for you as well

 

[Everz]

Edexcel.

*****.

My teacher has not taught us extension chemistry. The whole class has self taught over the last 2-3 days or so.

We're all going to fail.

Woohoo.

Only 3 exams left and something was BOUND to go wrong.

/emo

haha glad we werent the only ones who got fucked over, 2 months before the exam the teacher realised all we had been taught was alkanes and alkenes..

 

[swords]

Guess you got screwed then not much point me explaining it now I suppose, doh.