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# Chemistry Question Help Watch

1. (Original post by z1820)
It's 14 tonnes

It can't be 25 tonnes because that's the mass of Calcium Carbonate

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Okay, tell me how you got fourteen tonnes please.
I really dunno how to work it out.
2. (Original post by noor.m)
Dude! It's at 1:30, I should be sleeping but I just can't I have a feeling this paper will be hard Make sure to revise soluble salts! I heard that will be the 6 marker
Soluble salts are a breeze. Only thing I'm worried about is exo/endothermic thingies and quantitive chemistry
3. Mass= Mr x Moles
1. You need to calculate the mr of both cao and caco3.
2. 40+16= 56 (cao) 40+(16)3+ 12=100(caco3)
3. Divide the mass by mr to find the moles
4. Convert the tonnes to grams 25x1,000,000=25,000,000
5. 25,000,000/100= 250,000(moles of caco3)
6. As there is the same ratio of cao and caco3 moles remain the same.
7. 250,000x 56= 14,000,000

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4. Or 14 tonnes. Sorry.

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5. (Original post by CorpusLuteum)
Okay, tell me how you got fourteen tonnes please.
I really dunno how to work it out.

25 tonnes -------> ?
Mr: (adding all the relative atomic masses)
CaCo3----->CaO
100 ------> 56

What do you need to do to a 100 to get to 56? - X 0.56
So:
100 X 0.56 = 56

Whatever you do to the Mr, you do to the mass:

So 25 X 0.56 = 14 tonnes

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6. (Original post by z1820)
25 tonnes -------> ?
Mr: (adding all the relative atomic masses)
CaCo3----->CaO
100 ------> 56

What do you need to do to a 100 to get to 56? - X 0.56
So:
100 X 0.56 = 56

Whatever you do to the Mr, you do to the mass:

So 25 X 0.56 = 14 tonnes

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OOOOOH OH MY GOSH THANK YOU SO MUCH, makes so much sense.

!!!
7. (Original post by CorpusLuteum)
Soluble salts are a breeze. Only thing I'm worried about is exo/endothermic thingies and quantitive chemistry
I know! That and paper and gas chromotography are a god send

Okay so exothermic is when heat is given off to the surroundings (I think of it as exhale). If you put your hand on this it would feel warmer, people usually get confused with this, it feels warmer because the heat is going to the surroundings (your hand) So an example of exothermic for something we use everyday would be a hand warmer.
An endothermic reaction is something that takes in heat, so if you put your hand on it it will be colder because it's taking the heat from your hand , an example of this would be an ice pack! You have to know how to represent this on the graph and the advantages and disadvantages of a Ice Pack being disposable and non disposable!
8. (Original post by noor.m)
I know! That and paper and gas chromotography are a god send

Okay so exothermic is when heat is given off to the surroundings (I think of it as exhale). If you put your hand on this it would feel warmer, people usually get confused with this, it feels warmer because the heat is going to the surroundings (your hand) So an example of exothermic for something we use everyday would be a hand warmer.
An endothermic reaction is something that takes in heat, so if you put your hand on it it will be colder because it's taking the heat from your hand , an example of this would be an ice pack! You have to know how to represent this on the graph and the advantages and disadvantages of a Ice Pack being disposable and non disposable!
Ooooh. Thank you for clarifying this.

I have something to help you remember what molecules are diatomic so when you have to write an equation:

9. (Original post by CorpusLuteum)
Ooooh. Thank you for clarifying this.

I have something to help you remember what molecules are diatomic so when you have to write an equation:

Thank you! But what do you mean by diatomic? duuude it's nearly midnight we should be getting to sleep
10. (Original post by noor.m)
Thank you! But what do you mean by diatomic? duuude it's nearly midnight we should be getting to sleep
Diatomic are the elements that when written have a little two next to them.
I'll sleep later on once I've done enough revision seeing as the exam is later in the day.
:P

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