Chemistry: Post your doubts here!

[iKhaled]

i need serious help... :/

what carbonyl compound that contains both the OH group and the carboxylic acid group, for example..

(CH3)2C(OH)CO2H

 

[JD REBORN]

Q11) Notice the words in the question '[...]reaction between powdered aluminium and powdered barium nitrate in which heat is evolved[...]'. The formation of Al2O3 is a highly exothermic reaction.

Q13) I'm pretty sure that they're testing our knowledge of solubility. We know all nitrates are soluble, so C and D can't possible be the answer. Likewise for halides. Except for a chosen few (eg: AgCl), all halides are soluble. Hence, the only salt that CAN precipitate is CaCO3. Also, CO3^(2-) ion is more reactive than the Cl- ion (recall the order of displacement in electrolysis).

31) The Mr is 72. This means one of the Cl atoms has nucleon number 35 and the other one has nucleon number 37.
Since the number of electrons and protons determine the radius and they are not changing, the radius remains the same. The nucleon number changes. The isotopic mass also changes.

34) Bronsted Lowry acids are proton donors and B-L bases are proton acceptors. Salts may or may not be formed. Hence answer is D.

35) This is purely a question on the properties of MgO. You need to know them in order to answer this.

36) Thermal stability DECREASES. Recall how introducing a hot rod into a jar with HI decomposes it.
Bond length increases. This can also be seen from the Data Booklet. (Bond strength decreases; stronger bonds are shorter)
Ease of oxidation increases. Concentrated H2SO4 oxidizes HI to I2 but can not oxidize HCl.

thnx man i love u

 

[Jaf]

i need serious help... :/

what carbonyl compound that contains both the OH group and the carboxylic acid group, for example..

(CH3)2C(OH)CO2H

What? That's not a carbonyl compound.
Though if you're asking what carbonyl compound the given compound originally was before hydrolysis, then it was (CH3)2CO (i.e propanone)

 

[iKhaled]

What? That's not a carbonyl compound.
Though if you're asking what carbonyl compound the given compound originally was before hydrolysis, then it was (CH3)2CO (i.e propanone)

what do they call the compound i mentioned above?

 

[Jaf]

what do they call the compound i mentioned above?

2-hydroxy-2-methylpropanol

 

[USMAN Sheikh]

Jaf can u pls reply my ques bond angles one that is on previous pafge

 

[USMAN Sheikh]

Ooops, sorry. I misread the question.

NDH3Cl would produce NH3 or NH2D at best. It can_not produce ND3.

can u also pls elaborate each option aswell

 

[Nikesh]

any one pls q 2 aand 5 pls be quick

for 2 its B) Carbon as it has total of 2 electron pairs and and 2 unpaired electrons in 2 principle quantum orbital (Draw box electronic configuration to see that)
for 5) its C because double bond acts as a single bond pair...

 

[USMAN Sheikh]

for 2 its B) Carbon as it has total of 2 electron pairs and and 2 unpaired electrons in 2 principle quantum orbital (Draw box electronic configuration to see that)
for 5) its C because double bond acts as a single bond pair...

Cant it be B as trigonal planar(120) means 3 bonding pair hence there are 2 bonding and a lone pair which dec the anlgle a bit so it shld be around 109??/?

 

[JD REBORN]

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q6 and Q17

 

[USMAN Sheikh]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q6 and Q17

For 6 only paper and poly etherne are combustible hence option A and D gets cancel both B and C are eectrical insulator and but only polmers melt over range of temp !! its C

 

[namraahmad]

Aslamaliakum.....
Can you help me out in calculating retention time i mean is there any way to calculate it or its just read off from the graph??

 

[Student12]

How many structural and cis-trans isomers are there for dichloropropene, C3H4Cl2 ?
A 3
B 5
C 6
D 7
The answer is D! Can anyone draw all the 7, please ?

 

[Student12]

How many alcohols (including both structural isomers and stereoisomers) can have the molecular
formula C4H10O?
A 3 B 4 C 5 D 6
The answer is C can anyone draw and show ?

http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_s04_qp_1.pdf
Q- 9,18
http://www.xtremepapers.com/papers/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf
Q-3,10,19,23,31

Help would be appreciated =D

 

[Nibz]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s04_qp_1.pdf
Q- 9,18

Q9. Enthalpy Change = T.Enthalpy Change of formation of products - T.Enthalpy of formation of reactants
= -1676 - 3(-266)
= -878
Answer is B.


Q.18
Reaction for electrolysis of Brine 2NaCl + 2H2O --> 2NaOH + H2 + Cl2
Moles of NaCl used = 58500/ 58.5 = 1000 mol

NaCl and Cl2 are in the ration 2:1
So mass of Cl2 = 1000/2 x 71 = 35500 g = 35.5 kg

NaCl and H2 are also in the ration 2:1
Mass of H2 = 1000/2 x 2 = 1000g = 1 kg

NaCl and NaOH are in the ration 1:1
Mass of NaOH = 1000 x 40 = 40000g = 40kg

So Answer is A.

 

[UltimateHustla]

Thats not true if you do it well, you will be fine
I wasnt screwed, got a good grade

well i hope you are right cause i worked my ass off

 

[tom ed]

Yeah, I did get the answer. If you want, I'll put up a picture of how I did it (if you're THAT fond of getting shocks )

how is "wanting to know... how to get to a conclusion?" related to "being fond of getting shocks"....btw i also got the answer,thanks anyway!

 

[DPratik]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w08_qp_1.pdf
Q6 and Q17

in question number 6) as the question has mentioned as insulator which means the answer is either polyethene or silicon oxide....but the question has also said that the compound melts over a wide range of temperature which means the answer is obviously polyethene because silicon oxide has a high temperature and doesn't has variable melting temperature !!!

i question 17) there are few things which must be remembered,first chlorine is stronger oxidizing agent than sulphuric acid and H3PO4 is less oxdizing agent than iodine because when H3PO4 is treated with sodium iodide,acidic gas which shows that H3PO4 is a weak oxidizing agent,so after all this you have only one option left and i.e sulphuric acid is stronger oxidizing agent than iodine !!!

 

[panda222]

Question 5 on that page:

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w09_qp_11.pdf

Why isnt the answer C or A?

 

[imanmalik]

There are 4 chlorines in A. The resultant dipole is 0 because all 4 chlorines have the same electronegativities and cancel each other out. It's not C because the dipole formed by O and Cl cancel each other out due to their similar electronegativities. It's B because of the difference between the electronegativites of the O and H are different (the electronegativity of O is much greater than the electronegativity of H) So the O end is negative and the C-H2 end being positive