Chemistry: Post your doubts here!

[AbbbbY]

Also, guys, if you have OCRs in your PDF readers and it allows you to copy, please copy the question and put it here. So much quicker to solve that we! More questions can be solved that way and can solve even when short on time.

 

[Omar99]

Re: All Chemistry help here!! Stuck somewhere? Ask here!

tonnes of CHEMISTRY WORKSHHETS
http://www.chemactive.com/a_level_chemi ... tions.html

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
question no. 11 and 32

 

[AbbbbY]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s11_qp_12.pdf
question no. 11 and 32

11- Oo that's a tough one!

X is an Al C compound so Al(OH)3 and CH4 will be formed

X -> Al(OH)3 + CH4

CH4 + O2 -> 2H2O + CO2

CH4 : CO2
CO2 moles = 1.7 mol


Fk it man. Can't be this long a solutoin.
Eventually you'd get the answer by making each reaction balacing it's equation and seeing if the ratio of X:CH4 is that of the eqation but they can't take you that long in an MCQ I think it's a trap.

It has to be something simple in that case. My arrows point to Al4C3 because C has 4 outer electrons and Al has 3. Can't be this long.

What's the answer? Maybe someone else can correct me here if I'm wrong.


32:

1- Ideal behavior says it has negligible volume. This negates ideal behavior, hence true. Option C is eliminated.

2- My logic tells me this could be possible but 6000kPa is a measly 60atm and essentially the change is 45atm's. Would be too less to liquify a gas (given that NH3 exists as gas at 200atm). I know it's not an accurate measure. Tough call to rule this one out, but If I had to choose, I'd say it wasn't liquifying.

3- That's a ridiculous statement.

We're left with B and D. I'd pick D because of the pressure-vs-liquify logic I posted up there. But, that's just me. Can't open the marking schemes somehow. What's the answeR?

 

[Student12]

Some Doubts..
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_ms_1.pdf
Questions 1 , 3 , 10

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_ms_1.pdf Questions 8 , 9 , 26

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_ms_1.pdf Questions 1, 9 , 10

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_ms_1.pdf Questions 1,2,6,15,31

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_ms_1.pdfQuestions 1,2,4,30

I know these are aloot in one go.. but i need help! =)

 

[AbbbbY]

Some Doubts..
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s06_ms_1.pdf
Questions 1 , 3 , 10

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s07_ms_1.pdf Questions 8 , 9 , 26

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w07_ms_1.pdf Questions 1, 9 , 10

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_ms_1.pdf Questions 1,2,6,15,31

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdfhttp://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_ms_1.pdfQuestions 1,2,4,30

I know these are aloot in one go.. but i need help! =)

MJ 06
1
N2O4 : 2NaOH
0.02 mol : 0.04 mol

conc = mol / vol
0.5 = 0.04 / vol
vol = 0.08 dm3
Hence, D

3-

Nitrogen atom: 1s2 2s2 2p3
Ga3+ means it's losing 3 electrons, so Nitrogen becomes 1s2 2s2 2p6
Hence D

10:

Partial Pressure of Products: (2/3)(2/3)*1
Partial Pressure of Reactants: (1/3)*1

Divide them, you get 1.3 (since I had to do it on windows calc)
so that's 4/3 atm


MJ07

8-

By defination, Standard Enthalpy change of Formation is the energy change associated with the formation of ONE MOLE of a substance from it's constituent elements in standard states.

This reaction is the formation of 2 moles of Fe2O3 so enthalpy change / 2 = enthalpy of formation

Hence B

9-

For simplicity's sake over here, I'll write :
X2 = A
Y2 = B
X2Y = C

Reac 1: [C][C]/[A][A] = 2
Reac 2: [sqrtB][A]/[C]

Resolve them and you should get 1/2 or 1/sqrt2 don't have a paper please check and if you can't figure it out let me know


ON07P1

Q1

1 mol has 6.02x10^23 atoms
Mass of Ag = 0.216g
Mass of Ag per cm3 = 0.216/150 = 0.00144
Moles of Ag per cm3 = 0.00144/108 = 0.0000133
Atoms of Ag per cm3 = 6.02x10^23 * 0.0000133 = 8.023 x 10^13
so, A


The rest, I'll answer in the evening. Gotta rush.

 

[ahmed abdulla]

<?

 

[Mishaa]

<?

5. C
Due to a significant difference between the 5th and 6th IEs, it can be deduced that X is in Group V of the periodic table with charge -3. It will mst probably form a covalent chloride XCl3.

28. B
Dissolving occurs due to hydrogen bonding between hydrogens or its isotopes that are directly bonded to oxygen, nitrogen or flourine, with water molecules. In this case, hydrogens directly bonded to oxygen are to be replaced, so apparently there would be 3 replacements.

3. C
At room temperature, post reaction gases are unreacted O2, CO2 and SO2. No need to take molar ratios, gaseus ratios are taken. 30 cm3 of O2 is left after reacton (30 cm3 reacts with 10cm3 of the thiol), 10 cm3 each of SO2 and CO2 are produced. Total is 50 cm3.

 

[Mishaa]

thanks sooo much
can u help me with this ?

Send me the links to the question papers, I can't read a word here. I'm sorry.

 

[ahmed abdulla]

Send me the links to the question papers, I can't read a word here. I'm sorry.

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
q 10 , 12 , 18 & 37 38

 

[Student12]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s07_qp_1.pdf
Q 9-A ( Please could someone elaborate & explain)26-C

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w07_qp_1.pdf
Q 9- B 10-D (How did the 2.42 come)

 

[Student12]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf
Q 1D 2A 6C 15B 26C 31 2/3 are the right options.
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q 1A 2C 4C 30C

 

[Student12]

I have a major problem in chemistry calculations.. how do i solve this problem? :/

 

[ahmed abdulla]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
q 10 , 12 , 18 & 37 38

 

[Student12]

Someone answer!!

 

[h4rriet]

I have a major problem in chemistry calculations.. how do i solve this problem? :/

Practice questions.

 

[hela]

PLEASE HELP
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf Q6 C Q7 D Q26 C
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf Q 26 C
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w10_qp_12.pdf Q 8 D Q25 D

 

[zackle09]

Hello! can someone pls do this for me
http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

question 8...how do you solve it?

 

[Mairaxo]

Hello! can someone pls do this for me
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s10_qp_11.pdf

question 8...how do you solve it?

use all elements Ar given. Replace X using the elements given and find the mole ratio!

 

[Mairaxo]

PLEASE HELP
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdf Q6 C Q7 D Q26 C
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf Q 26 C
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf Q 8 D Q25 D

May June 2008 - Q7 - Aluminium is a metal so metalic bond but phosphoros is a non metal and has covalent bonds so not A. Argon is monatomic and chlorine is diatomic so not B. Magnesium is a meta sulphur is non metal so different bonds. Sulphur and chlorine are both non metals with covalents bonds between atoms so its D

 

[Mairaxo]

PLEASE HELP
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s08_qp_1.pdf Q6 C Q7 D Q26 C
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf Q 26 C
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf Q 8 D Q25 D

May 2008 - Q26 - the alcohol is HO-CH2-CH2-CH2-CH2-OH. This is becaus only primary alcohols get oxidised to acids. secondry and tertiary alcohols dont. hence OH is at 1st and 4th carbon so its C.