Edexcel IAL Chemistry Unit 1 (WCH01 )/ May 27 June 2016

OP

Original post by imnoteinstein

thanks but i think the reason is that c2h5 doesnt exist haha! nothing suggests which ones molecular but the fact that c2h5 isnt a thing :' :wink:

OMG! I didn't even notice that! :facepalm:

Reply 63

imnoteinstein

2

Original post by Sandy_Vega30

OMG! I didn't even notice that! :facepalm:

sorry for so many questions but here
https://110d0b1a7b584219c71ba4cfe896ad1711fa3ef7.googledrive.com/host/0B1ZiqBksUHNYR00tYjdZN052azQ/January%202015%20(IAL)%20QP%20-%20Unit%201%20Edexcel%20Chemistry.pdf
Q22b iii, why do we multiply by 2 to find enthalpy change of reaction/ mole?

Reply 64

zahragoli97

3 A hydrocarbon contains, by mass, 82.7% carbon and 17.3% hydrogen.The molecular formula of the hydrocarbon is A CH3

1.

B C2H6

2.

C C2H5

3.

D C4H10
I found the empirical formula and its C, but why the answer is D??Why the empirical formula just be same as the molecular?

Reply 65

Just a quick question, what is an acceptable definition of a sub shell?

Reply 66

zahragoli97

Which of the following enthalpy changes cannot be measured directly by experiment?
The enthalpy change of

1.

A formation of methane.

2.

B combustion of hydrogen.

3.

C formation of carbon dioxide.

4.

D combustion of carbon monoxide.

why A?

Reply 67

Original post by zahragoli97

3 A hydrocarbon contains, by mass, 82.7% carbon and 17.3% hydrogen.The molecular formula of the hydrocarbon is A CH3

1.

B C2H6

2.

C C2H5

3.

D C4H10
I found the empirical formula and its C, but why the answer is D??Why the empirical formula just be same as the molecular?

The empirical formula is C (molecular mass = 29). The molecular formula may have been D because the molecular mass may have been 58.

Reply 68

imnoteinstein

2

Original post by zahragoli97

3 A hydrocarbon contains, by mass, 82.7% carbon and 17.3% hydrogen.The molecular formula of the hydrocarbon is A CH3

1.

B C2H6

2.

C C2H5

3.

D C4H10
I found the empirical formula and its C, but why the answer is D??Why the empirical formula just be same as the molecular?

its D because c2h5 doesnt exist

Reply 69

zahragoli97

1.

In an experiment, 3.425 g of lead oxide was reduced to form 3.105 g of lead.The empirical formula of the lead oxide is A PbOB Pb3O2C Pb3O4D Pb4O3

how to do this question??

Reply 70

Original post by imnoteinstein

its D because c2h5 doesnt exist

aah i see lol

Reply 71

katenell

4

https://110d0b1a7b584219c71ba4cfe896ad1711fa3ef7.googledrive.com/host/0B1ZiqBksUHNYR00tYjdZN052azQ/June%202014%20(IAL)%20QP%20-%20Unit%201%20Edexcel%20Chemistry.pdf
answers for with explanation please i know i am bet late but please
Q4
q8
q9
q10
q11
q14
q16

Reply 72

Bliss_

Original post by zahragoli97

Which of the following enthalpy changes cannot be measured directly by experiment?
The enthalpy change of

1.

A formation of methane.

2.

B combustion of hydrogen.

3.

C formation of carbon dioxide.

4.

D combustion of carbon monoxide.

why A?

its a how science works question.
the reason is the enthalpy of combustion of all hydrocarbons can not be measured directly.
and its A cause methane is a hydrocarbon. :smile:

Reply 73

OP

Original post by zahragoli97

3 A hydrocarbon contains, by mass, 82.7% carbon and 17.3% hydrogen.The molecular formula of the hydrocarbon is A CH3

1.

B C2H6

2.

C C2H5

3.

D C4H10
I found the empirical formula and its C, but why the answer is D??Why the empirical formula just be same as the molecular?

Refer to page 2. The same question was discussed earlier. :smile:

Reply 74

Original post by katenell

https://110d0b1a7b584219c71ba4cfe896ad1711fa3ef7.googledrive.com/host/0B1ZiqBksUHNYR00tYjdZN052azQ/June%202014%20(IAL)%20QP%20-%20Unit%201%20Edexcel%20Chemistry.pdf
answers for with explanation please i know i am bet late but please
Q4
q8
q9
q10
q11
q14
q16

Q4 B has an unpaired electron in the 2p subshell. So it's further away from the nucleus than Be's electrons (which are in the 2s subshell and are closer to the nucleus).
Q8 88/44= 2 mol of CO2 27/18= 1.5 mol of water therefore 4 mol of CO2 and 3 mol of water. So from this you can see that there will be 4 carbons and 6 hydrogens so the answer is C, C4H6
Q9 This is a definition you just have to learn, Avagadro constant refs to atoms in one mol of any monatomic element
Q10 8.5/(14+3) = 0.5 mol 15/30= 0.5 mol so 0.5 mol forms 0.5 mol so its 100%
Q11 55/1000 * 0.2 = 0.011 mol... 0.011*143.4 = 1.58g
Q14 draw them out with displayed formula and you will see why its C2F4
Q16 draw the hess's cycle then you will see that the calculation will be -572-(-484) = -88. But this is for 2 mol so for 1 mol its -44 KJmol-1

Reply 75

OP

Original post by Bliss_

its a how science works question.
the reason is the enthalpy of combustion of all hydrocarbons can not be measured directly.
and its A cause methane is a hydrocarbon. :smile:

A is "Formation of Methane"., not combustion. Now, how would you explain this? :redface:

Reply 76

OP