Chemistry: Post your doubts here!

[donor]

help with question 11 please. http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Can someone pls answer this? second time I'm posting.

 

[Muhammad Bin Tahir]

What is a dimer?

 

[Vui Loong]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_w06_qp_1.pdf No 9
http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s05_qp_1.pdf No 7
Anyone please explain me to this?

 

[smartangel]

answer for 8 is D
atomisation energy+first ionisation energy+ second ionisation energy + enthalphy change of hydration
177+590+1150-1565=352


answer fo 13 is B
have to use trial and error method, that is try putting all options

umm but it sayd use oxidation numbers for 13.so im sure there is a way other than trial n error

 

[saudha]

The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide,
Al2O3(s), are –266kJmol–1 and –1676kJmol–1 respectively.
What is the enthalpy change under standard conditions for the following reaction?
3FeO(s) + 2Al(s)
3Fe(s) + Al 2O3(s)
A +878kJ B –878kJ C –1942kJ D –2474kJ

i get the opposite charges alwayss..... how do i get it right?

 

[smartangel]

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Q34..after 20 mins rxn is complete..mass of mg used is same so how can sukfuric acid produce more gas? statement 3 is correct according to ms..how?

 

[samwickz]

http://www.xtremepapers.com/CIE/International A And AS Level/9701 - Chemistry/9701_s07_qp_1.pdf
Q no 1 that mass spectro thingy any 1 who could help me pretty plz

 

[smartangel]

Use of the Data Booklet is relevant for this question.
In an organic synthesis, a 62% yield of product is achieved.
Which of these conversions are consistent with this information?
1 74.00g of butan-2-ol → 44.64g of butanone
2 74.00g of butan-1-ol → 54.56g of butanoic acid
3 74.00g of 2-methylpropan-1-ol → 54.56g of 2-methylpropanoic acid
plz do working for this one..all 3 statements are correct!

 

[Casablanca]

The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide,
Al2O3(s), are –266kJmol–1 and –1676kJmol–1 respectively.
What is the enthalpy change under standard conditions for the following reaction?
3FeO(s) + 2Al(s)
3Fe(s) + Al 2O3(s)
A +878kJ B –878kJ C –1942kJ D –2474kJ

i get the opposite charges alwayss..... how do i get it right?

I got B. Is that the correct answer?

 

[angelicsuccubus]

Hey guys... Is there anyone willing to come online and do a past paper with me? I haven't done any chem all year long and I can't seem to answer shit! Freaking out here >.<

 

[Casablanca]

Hey guys... Is there anyone willing to come online and do a past paper with me? I haven't done any chem all year long and I can't seem to answer shit! Freaking out here >.<

There's two guys already doing that. The thread all the way at the bottom of the page.

 

[lavanyamane]

What is a dimer?

2 molecules of the same compound. Eg: Al3Cl6 is a dimer of AlCl3

 

[umarashraf]

2 molecules of the same compound. Eg: Al3Cl6 is a dimer of AlCl3

you really confirm...???

 

[lavanyamane]

you really confirm...???

Yes

 

[00tanveer]

Can anyone please solve O/N 09 no.21???? Would be very grateful...

 

[umarashraf]

Yes

waoo.. i knew from ages that al2cl6 is a dimer.. but never knew why...

 

[saudha]

I got B. Is that the correct answer?

yah but hw did u do it?

 

[samwickz]

Use of the Data Booklet is relevant to this question.
Oxides of nitrogen are pollutant gases which are emitted from car exhausts.
In urban traffic, when a car travels one kilometre, it releases 0.23 g of an oxide of nitrogen NxOy, which occupies 120cm3.
What are the values of x and y?
(Assume 1 mol of gas molecules occupies 24.0dm3.)

A x = 1, y = 1
B x = 1, y = 2
C x = 2, y = 1
D x = 2, y = 4

so is it correct if i do the sum lyk this

n=(120*10^-3)/24
=5*10^-3

(5*10^-3)=0.23/mr
mr=46

(14*1)+(16*2)=46

am i ryt or is there a diff way 2 get it done?

 

[Osake]

Can someone help me do Question 24 on the winter 2005 paper 1 question? , What the easiest way to approach this question? I got how to do it , but similar questions always come , Whats the deal with teritiary alcohols , can they only form 2 different alkenes or what?

 

[umarashraf]

The standard enthalpy changes of formation of iron(II) oxide, FeO(s), and aluminium oxide,
Al2O3(s), are –266kJmol–1 and –1676kJmol–1 respectively.
What is the enthalpy change under standard conditions for the following reaction?
3FeO(s) + 2Al(s)
3Fe(s) + Al 2O3(s)
A +878kJ B –878kJ C –1942kJ D –2474kJ

i get the opposite charges alwayss..... how do i get it right?

you still have this problem or its solved now...???