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# Current Year 12 Thread Mark I (2012-2013) watch

1. (Original post by kishihime)
Here's a question we did earlier today where I got confused if you don't mind.

a.) Petrol is basically octane (C8H18).
An average small car travels 10 000 miles a year. The fuel consumption is 7.5 miles per litre of petrol. 1 litre of petrol has a mass of 1000g.
What volume and mass of CO2 does this car produce in a year?

Anyway, mole ratio is 1:8

If you don't mind, could you explain the steps? We did it this morning so I know you have to convert stuff to moles but I don't understand why or how.

And if anyone can help me with Physics. I'm a little bit confused as to how I'm supposed to calculate the displacement. It's basically distance, right? So would it just be v*t? Apparently I have to calculate the area of the triangle on the graph, not sure if this is right.

Sorry for asking for so much
I'm really sorry, I was just doing my biology homework. But I see usy has helped you. Do you understand it?
2. (Original post by usycool1)
Gosh!

No problem at all!

If you don't mind checking what I've done for a different question.

- If we have been given 0.24g of Mg. What volume of a 0.01 moldm^-3 of HCl is needed for complete reaction?

So I got... Concentration = 0.01 moldm^-3 Mass = 0.24g Volume = ? Mole ratio = 1:2

I converted the mass of Mg into mols with Mols=Mass/Ar
0.24/24 = 0.01

For mols of HCl I just multiplied the above with mole ratio.
0.01 x 2 = 0.02

I got that far, I'm not sure what to do.
3. (Original post by kishihime)

If you don't mind checking what I've done for a different question.

- If we have been given 0.24g of Mg. What volume of a 0.01 moldm^-3 of HCl is needed for complete reaction?

So I got... Concentration = 0.01 moldm^-3 Mass = 0.24g Volume = ? Mole ratio = 1:2

I converted the mass of Mg into mols with Mols=Mass/Ar
0.24/24 = 0.01

For mols of HCl I just multiplied the above with mole ratio.
0.01 x 2 = 0.02

I got that far, I'm not sure what to do.
Looks good, now you can use the forumula:

Number of Moles = (Concentration x Volume)/1000 to work out the volume of HCl.
4. (Original post by usycool1)
Looks good, now you can use the forumula:

Number of Moles = (Concentration x Volume)/1000 to work out the volume of HCl.
I'm being stupid since it's late. How would I rearrange the formula to find the volume instead?
5. (Original post by kishihime)
I'm being stupid since it's late. How would I rearrange the formula to find the volume instead?
Multiply both sides by 1000 and then divide by the concentration.
6. (Original post by usycool1)
Multiply both sides by 1000 and then divide by the concentration.
OH.

I got Volume=(1000xMols)/Concentration

So (1000 x 0.02)/0.01 = 2000dm^3, which is apparently correct!

Thank you so much, I really appreciate the help. I hope I didn't bother you too much. I'll be off now, so good night!
7. (Original post by usycool1)

Do you stay on TSR 24/7 !?

8. my teacher gave me the dissappointed look today in biology because I got an A not an A* on a piece of homework (I missed it by 2 marks )
9. (Original post by lilGem)

my teacher gave me the dissappointed look today in biology because I got an A not an A* on a piece of homework (I missed it by 2 marks )
That's what you get for setting high standards.
10. (Original post by lilGem)

my teacher gave me the dissappointed look today in biology because I got an A not an A* on a piece of homework (I missed it by 2 marks )
Lol, why would she be disappointed if you got an A?
11. (Original post by Tullia)
That's what you get for setting high standards.
True, I mucked up the essay big time though
12. (Original post by Ndella)
Lol, why would she be disappointed if you got an A?
Ah I have this reputation as a "star of the biology department" and have gotten an A* in bit of homework so far. . .so he started to expect that from me
13. (Original post by lilGem)
Ah I have this reputation as a "star of the biology department" and have gotten an A* in bit of homework so far. . .so he started to expect that from me
Aww... I'd rather disappoint than be thought of as low standard and get higher but not gey attention xD

Posted from the Bottom of the Big Blue Sea...
14. (Original post by lilGem)
Ah I have this reputation as a "star of the biology department" and have gotten an A* in bit of homework so far. . .so he started to expect that from me
Ah, it was only 2 marks so he should be happy
Aww... I'd rather disappoint than be thought of as low standard and get higher but not gey attention xD

Posted from the Bottom of the Big Blue Sea...
I can't help my standards, unfortunately in my AS subjects it's the same story

(Original post by Ndella)
Ah, it was only 2 marks so he should be happy
True, I'm slightly dissappointed in myself though
16. (Original post by lilGem)
I can't help my standards, unfortunately in my AS subjects it's the same story

True, I'm slightly dissappointed in myself though
How so??

Posted from the Bottom of the Big Blue Sea...
How so??

Posted from the Bottom of the Big Blue Sea...
We've been set a few homeworks on them and my %age is fairly similar
18. (Original post by lilGem)
We've been set a few homeworks on them and my %age is fairly similar
I don't understand how you can get an A* on pieces of work though

I mean it's not the whole subject thing? And it's only one piece and that one piece won't be all thats on the exam? :,0

Posted from the Bottom of the Big Blue Sea...
19. (Original post by lilGem)
True, but the large number of medics/ dentists/ vet meds/ oxbridge success stories
yeah I agree there is a lot about that, but its a forum based on academics what do you expect
I don't understand how you can get an A* on pieces of work though

I mean it's not the whole subject thing? And it's only one piece and that one piece won't be all thats on the exam? :,0

Posted from the Bottom of the Big Blue Sea...
I mean %age wise it's equivalent to what would be an A*, they use past paper questions for our homework

Nope, but thus far it's 2 fairly chunky topics

(Original post by BC95)
yeah I agree there is a lot about that, but its a forum based on academics what do you expect
True

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