IGCSE CHEMISTRY DOUBTS HERE !!!!

[elemis]

Before posting your IGCSE Chem doubts here, have a look in this thread and this one. Also try this one

Some good Paper 3 notes over here.

Use the search function in that thread to see if your doubt has already been answered.

If it hasn't then post here and someone will help you.

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1. The Year and session.
2. The Question number/part you have doubt in.

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Check THIS for Resources =D

Thank you =)

[$H00t!N& $t@r]

helllo ppl
i have some questions on the mole concept.. can someone please help.

1)Consider the combustion of pentanol: 2C5H11OH + 15O2 ---> 10CO2 + 12H2O
(a) How many grams of carbon dioxide are formed for each mole oxygen consumed?
(b) How many grams of carbon dioxide are formed for each gram of pentanol burned?

2) What mass of iron (iii) oxide will be produced by the complete oxidation of iron? 
 
 
 

[Vin]

Do you have the answers? I just want to be sure my solutions are correct.

[$H00t!N& $t@r]

Do you have the answers? I just want to be sure my solutions are correct.

yeah i do
1) (a) 29.3g
    (b) 2.49g

2) 143g

[$H00t!N& $t@r]

hello? percy jackson???

[Vin]

Oh I'm really sorry. I'm afraid I don't know the 2nd one.

1) a)

2C5H11OH + 15O2 ---> 10CO2 + 12H2O

Molecular mass of CO2 = 12 + 32
= 44 g

molar ratio of

    CO2 : O2  
    15 : 10
      1 : x

so, x = 10/15

Mass of CO2 = 10/15 * 44
= 29.3 g

b) Ratio of

  pentanol : CO2
          2 : 10
           1 : x
so for 1 mole, x = 5

Therefore 1 mole of pentanol = 5 moles of CO2 is formed
= 44 * 5
= 220 g

Now, you gotta find for 1 gram of pentanol

Mass of pentanol = 60 + 11 + 16 + 1
= 88g.

So,  
Pent.   CO2
88g      220g
1g         x

x = 220/88
= 2.5 g

[$H00t!N& $t@r]

thanks alot for the detailed answer!  as for no. 2 i'll try to figure it out 

[Vin]

thanks alot for the detailed answer!  as for no. 2 i'll try to figure it out 

You're welcome. Hope you got it. It's a bit crude. I'll ask my teacher too tmw.

[Vin]

yeah i do
2) 143g

Are you sure about the answer? Also is the question you know, complete?
It should be 80g according to me. :\

[Deadly_king]

2C5H11OH + 15O2 -----> 10CO2 + 12H2O

a) According to the equation :
15 moles of oxygen are required to produce 10 mole of carbon dioxide
15 moles of oxygen are required to produce (10 x44)g of carbon dioxide ( Mr of CO2 = 44)
Therefore 1 mole of oxygen will produce (10 x 44)/15 = 29.3g of CO2

b) According to the equation :
2 moles of pentanol burns to form 10 moles of carbon dioxide
(2 x 88)g of pentanol burns to form (10 x 44)g of carbon dioxide (Mr of pentanol = 83)
1g of pentanol will therefore burn to form (10 x 44) / (2 x 88) = 2.5g of CO2

2) 4Fe + 3O2 ----> 2Fe2O3

According to the equation :
For complete oxidation to take place, 4 moles of Fe reacts with 3 moles of O2 to form 2 moles of Fe2O3
1 mole of Fe reacts with 3/4 moles of O2 to form 1/2 moles of Fe2O3
1 mole of Fe reacts with 3/4 moles of O2 to form (1/2 x 159.6)g of Fe2O3
Mr of Fe2O3 = 159.6

Mass of iron (iii) oxide formed upon complete combustion of 1 mole of Fe = (159.6/2) = 79.8g

I agree with Percy.

Hey shooting star......u asked the same question here (https://studentforums.biz/sciences-149/chem-mole-calculation-plz-help/msg349416/#msg349416)

[HUSH1994]

i dont get chromotography at all :S

[elemis]

i dont get chromotography at all :S

Hang on.

[elemis]

http://www.docbrown.info/page04/OilProducts13.htm

Read carefully.

[elemis]

http://www.docbrown.info/page01/ElCpdMix/EleCmdMix2.htm#Chromatography

This also.

[Adzel]

Can someone please answer this for me...