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Chemistry Revision Thread

OP

I do AQA (coordinated) double science.

Well, that's just it - what the heck is the organism?? It's referring to industrial processes of enzymes, so in order to make a continuous process rather than a batch process, they a) immobilise the enzyme by trapping it etc and b) stabilise the organism to keep it functioning for long periods. Hmm.. maybe it means yeast or bacteria or something? :s-smilie:

Confuzzled

Reply 61

arpeggio

12

I really don't know. Enzymes are used as catalysts in biological systems, which might be where the organism thing comes in e.g. in fermentation, the fungus (is it a fungus?!) yeast is used, to produce the enzyme zymase in order to catalyse the reaction. I suppose the organism could be referring to yeast in this case then - 'keep it functioning' i.e. keep it producing zymase?

(This is a complete guess in case you hadn't noticed!)

Reply 62

Krystal

1

well 'stabalise' could mean keep growing at constant rate? aka reproducing...budding (wateva they do) so that the production of enzyme is constant as well?....just a thought really.

Reply 63

AliciaK

I need to revise, so if it's OK with everyone, I'm going to give another question! :smile:

Describe how you would carry out a flame test on a solid.

Reply 64

InterAdriano

Ok im stuck on this question in a test:

The equation for the reaction between iron and dilute sulphuric acid is

Fe + H2SO4 --> FeSO4 + h2

in the reaction 0.56g of iron reacted with dilute sulphuric acid, calculate the mass of iron [II] sulphate (FeSO4) formed.

H=1 o=16 s=32 fe 56

Help please lol

lol n da second part of da question :

Calculate the volume of hydrogen gas produced.

1 mole of hydrogen gas has a volume of 24dm3 at room temperatrure and pressure

Help lol

:suitc:

InterAdriano

Reply 65

Krystal

1

dip/ put solid on platinum wire into solid and expose to bunsen flame for solids (air-hole closed?).....gosh i never thought about HOW to do it. is that right?

EDIT: urm...calculate mass of hydrogen divide it by the RAM and multiply with the avogado constant 24 dm3....i think im right...can anyone check... sory.

Reply 66

AliciaK

Krystal

dip/ put solid on platinum wire into solid and expose to bunsen flame for solids (air-hole closed?).....gosh i never thought about HOW to do it. is that right?

My chem teacher is very exact :P

- take nichrome wire, sand it
- heat it on the Bunsen burner
- dip it in hydrochloric acid
- dip it in substance
- put it in flame
- observe colour

Reply 67

JayG99

Aggressive revolutionary!

1.7 litres= 1.7 dm (cubed).

1 mole of gas equals 24 dm(cubed) therefore moles of oxygen = 1.7/24.

=0.071 moles of O. Mass of O equal 0.071 mutliplied by 16= 1.13grammes.
Then look at the equation 2Mg + O2 = 2MgO.
32 grammes of O will give 40 grammes of MgO.
therefore 1 gram of O gives 40/32 MgO
so 1.13 grammes of O gives 40/32 multiplied by 1.13 multiplied by 2(account for moles) = 2.825 grammes

So 2.825 grammes of MgO produced.

Is that right? Let me know where i went wrong if i am. That was a long q is it a past q?

I got you 5.65 g, which is twice your answer, because instead of 0.71 x 16, i did 0.71 x 32, because oxygen is diatomic, and also, i used 80 grams of MgO instead of 40 because there's a 2 infront of the MgO. Am i wrong here?

Reply 68

davidjones90

12

It would be great if someone explains the answer to question 19a ii on the 2003 AQA 3421 H paper?

I know the answer but dont have a clue about it...I always though concentration is measured in dm^3 per mole.

Reply 69

chriztina27

14

c)Look at the table. It shows the results for burning 2g of ethanol and heating 100g of water:
fuel: ethanol
temperature at start: 20 degreesC
temeperature at end: 46 degreesC

Calculate the amount of heat transferred.

(Specific heat capacity of water is 4.2 J/ g degreesC

Answer: ????????

Reply 70

roweski

1

I could be mistaken but isn't that physics extension work christinaz? When i said moles of a solute, i meant how to calculate the moles in a solute. Does that sound right?

Reply 71

Aggressive revolutionary!

I got you 5.65 g, which is twice your answer, because instead of 0.71 x 16, i did 0.71 x 32, because oxygen is diatomic, and also, i used 80 grams of MgO instead of 40 because there's a 2 infront of the MgO. Am i wrong here?

Oh crap ye ur right. I did account for the 80 of the 2MgO when did 40/32 times 2. But i forgot about the diatomic oxygen which i went back and chagnged and still forgot. That is why urs is twice my answer (and is the correct answer). That was a good question.

Reply 72

Excalibur

OP

15

Could someone put my mind at rest? Do we need to know about molarity in solution etc for Double Award?

And another query: how can you define what a batch and continuous processes are?

Reply 73

Tonton Zola Moukoko

Gah, only thing that I'm not sure on is titrations. I think I'll just concentrate on everything else, its only 5 marks or so. Unless someone here wants to explain as much as they can for me, I'm sure they'll be better than my text boon and exercise book at explaining it :p:

Reply 74

arpeggio

12

Everything that's C7 or C8 on the specification is for the extension paper i.e. triple science only (but that's Edexcel - although if you do another exam board then I'm sure it's the same kind of thing. Have a look at your specification and see what it says.) Titrations... I actually quite like them (ah, what a geeky thing to say :p:

) They're a bit like moles really - once learned, they're not that bad! I'll try explaining them once I've had another look over my notes :smile:

Reply 75

roweski

1

Titrations are used mainly to get a reaction to only happen until neutralisation. E.g. you have to reactants, one in the titration tubey thing (A) and the other in a flask (B). Indicator is added to the flask so as to tell what is happening with its pH levels. A is released slowly from the titration tube and only stopped after neutrilisation, the approximate volume of A added is noted and the experiment set up again. This time titration tube is stopped or slowed down usually about 3/4 of the amount that was noted earlier. Then small increasements are added to ensure point of neutrilisation is accurate.

As for excalibur, well i think its only OCR extended paper :s its here just in case :wink:

(volume x concentration) / 1000

Reply 76

Tonton Zola Moukoko

roweski

Titrations are used mainly to get a reaction to only happen until neutralisation. E.g. you have to reactants, one in the titration tubey thing (A) and the other in a flask (B). Indicator is added to the flask so as to tell what is happening with its pH levels. A is released slowly from the titration tube and only stopped after neutrilisation, the approximate volume of A added is noted and the experiment set up again. This time titration tube is stopped or slowed down usually about 3/4 of the amount that was noted earlier. Then small increasements are added to ensure point of neutrilisation is accurate.

As for excalibur, well i think its only OCR extended paper :s its here just in case :wink:

(volume x concentration) / 1000

Thanks

What about Titration calculations, they seem to be what they mainly ask about, on AQA Modular anyway.

I've only been able to do them once I think, and quite luckily that was in the Module exam :biggrin:

Reply 77

roweski

1

burette!!! thats the tubey thing :wink:

and A is called a titrant, B is the analyt solution. Infact heres the site, they could explain it better than i ever could . . .
http://en.wikipedia.org/wiki/Titration

Reply 78

roweski

1

Does anyone know how to tell what is ionic or a covalent bond? Is it the group the components are in? Eg. NaCl, is ionic because sodium and chlorine are both need to gain/loose electrons.

Reply 79

Excalibur

OP

15

Ionic is between non metals and metals, while covalent is usually between non metals only. I think so, anyway.

Thanks for the molarity thing. :smile:

Anyone know what batch/continuous processes are?

Chemistry Revision Thread

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