Chemistry P1 Help

[beacon_of_light]

q10: At low temp, area L will increase since at low temp more molecules have low speeds...while N too will decrease as no of molecules with energy greater or equal to activation energy are less at low temp...

q34: if pressure on left side of U tube increases, mercury on RHS will rise...pressure is directly proportional ti no.of molecules...only equilibrium 1 shows an increase in no of molecules since forward reaction is endothermic and would favour forward reaction....

q37: endothermic reactions donot occur spontaneously but at high temperatures since they have high activation energies///and here Nitrogen has a high bond energy .

q40: esters undergo acid or alkaline hydrolysis...only in option 1 is an acid present....which will carry out acid hydrolysis...

 

[flyingcrayons]

Yup, what beacon_of_light said

June 2003 Q20 and Q33, please? I never know how to do questions about isomers. Any advices?

 

[beacon_of_light]

Now before gng for teh answers...a lil information!!!

There r two types of isomerism: Structural and stereo...

Structural is further divided into Chain, position or functional group isomerism.

Chain isomerism is when you differ chain lengths adding methyl groups eg...it can be either butane or 2-methyl butane!

Position isomerism is when you change the position of the same functional group..eg it either pentan-1-ol or pentan-2-ol

Functinal group isomerism is when you change functional groups....carboxylic acids have esters as their isomers, alcohol with ethers and aldehydes with ketones...

eg...CH3COOH has HCOOCH3 as its isomer...

Stereoisomers is further catogarized to geometric and optical isomerism. Geometric is cis-trans isomerism...while optical is when a chiral carbon atom is present...

Now draw all the possible isomers under these catogeries....

 

[beacon_of_light]

Q20: there would be five structural isomers and 2 cis-trans......

structural would be 1, 2 dichloroprepene...1,3....2,3.....3,3...1,1...and two cis trans..in total 7....

q33:ive already answerd this...see in the relevant post...cos i dont remember

 

[British Council]

Beacon dude, about Q.37 June 2007 which u answered last night..... The question reads Nitrogen and Oxygen react to form Oxides of Nitrogen... Isn't bond forming an exothermic process????????? If yes then wt made u think that the assertion "the reaction is endothermic" is correct... Moreover, about q.34 June 2007 in options 1 and 2 both the reactants and products are gases. Raising the temperature would shift the equilibrium to the backward direction as in option 2 that gas should theoretically exert a pressure on mercury, shouldn't it?? I M CONFUSED PLZZZZ HELP....

 

[beacon_of_light]

Beacon dude, about Q.37 June 2007 which u answered last night..... The question reads Nitrogen and Oxygen react to form Oxides of Nitrogen... Isn't bond forming an exothermic process????????? If yes then wt made u think that the assertion "the reaction is endothermic" is correct... Moreover, about q.34 June 2007 in options 1 and 2 both the reactants and products are gases. Raising the temperature would shift the equilibrium to the backward direction as in option 2 that gas should theoretically exert a pressure on mercury, shouldn't it?? I M CONFUSED PLZZZZ HELP....

Look nitrogen's bond enthalphy is VERY large so a large amount of energy is absorbed to break it..so the reaction is endothermic!!!here bond breaking enthalpy is high than bond formation enthalpy..try calculating it !!!

And read tht again..i wrote pressure here depends on no of moles..since in reaction 2 no of moles remain constant whether reaction proceeds forward or bacward...so no effect on the level of mercury!!! while N2 is totally out of choice! Agae samaj!!

 

[beacon_of_light]

And since the question says that volume of R is twice that of S...so presuree exertion is nullified due to diff..in volumes!

 

[British Council]

oooooooooooh k I get it thanks man...

Dude, can u please explain Nov 2006: Q.2, Q.9, Q.14 Q.19 Q.24 and Q.32....???

 

[British Council]

@ Beacon plzzzzzzzzzzzzzzzzzzz explain the following as well.....

Nov 2007: Q.8,Q.9, Q.32, Q.33 and Q.37....

Btw, does ENTHALPY CHANGE OF ATOMISATION ALWAYS INVOLVE A CHANGE FROM SOLID OR LIQUID TO GAS... CAN'T IT BE GAS MOLECULES TO GAS ATOMS???? Please elucidate...

Sorry to cause u so much trouble but I suck BIG TIME IN CHEM MCQS... :-S

 

[beacon_of_light]

enthalphy change of atomisation is when 1 mol of atoms is formed from an element in its STANDARD STATE...if its sodium, it would be a solid, if its bromine, it would be a gas....

for the rest of the questions i'll answer them...just wait on!

 

[beacon_of_light]

oooooooooooh k I get it thanks man...

Dude, can u please explain Nov 2006: Q.2, Q.9, Q.14 Q.19 Q.24 and Q.32....???

Q2: Na would have lowest 1st ionisation energy so its gone...Nw Nitrogen's also gone cos it would have the highest 1st ionisation eenrgy cos of partially filled p-orbital!

we r left with C and F: F has two electron pairs in its p-orbital ...so its ionisation energy would be lower thn N ....

q9: draw a hess cycle n solve this question...add O2 to both sides of equation to make CO2 and H2O...then following the arrows n enthalpy changes and using -44 as(+44)

cos water formed is in liquid state but v have to find it in gaseous state....

q14: make an equation of the decomposition of a group II nitrate...let the unknown metal be M

2M(NO^3)2 :arrow: 2MO2 + 4NO2 + O2

moles of metal nitrate = 5/ Mr of metal nitrate ...take Mr of M as x....

mass of MO2 formed = 5- 3.29 grams =1.71g
Moles of metal oxide= 1.71/(x+32)

equate both moles,you'll get x .....

q19: It is a fact!!!

q24: all others contain C-H bonds so they r flammable...O2 is left! thats the answer!!!

q32: only 1 is correct because both equations show a high H+ conc...since H2SO4 and HSO4- dissociate to produce protons...and therefore, sulphate ion conc will be low...comparatively with protons!!!

 

[flyingcrayons]

Thank you very much! Kudos to you, beacon_of_light.

How about November 2003 Q20 and Q30?

 

[beacon_of_light]

Thank you very much! Kudos to you, beacon_of_light.

How about November 2003 Q20 and Q30?

for qs no 20: keep on trying n u'll get the right answer ....there r four structural and 1 stereo....butan 1 ol ...butan 2 ol 2-methyl butan 1 ol and 2-methyl butan 2 ol....now although we shuld have counted 2 stereo but since one goes in structural donot double count it!!!just count the other mirror image!!!

q30: only ethanol n ethanoic acid mix with water....but ethanol doesn't react with NaOH..so answer is A...

 

[flyingcrayons]

Thanks You could be a teacher! Are you one? Lol

November 2004 Q39?
June 2005 Q21?

XD

 

[beacon_of_light]

Thanks You could be a teacher! Are you one? Lol

November 2004 Q39?
June 2005 Q21?

XD

Lol.no, am an As student!

q39: as it has OH groups, it will react with Na. and since there is no H alongside OH..no dehydration...n its molecular formula is its empirical formula.C5H12O4.....

q21: Now both compounds in step 1 have same no of carbon, hydrogens and fluorines....so its isomerisation...same molecular formula buh diff structural formula...

 

[flyingcrayons]

Wow, you're too good! Thanks again.

Alright, I have more questions.. I'll post all of them here and you guys can take your time to respond. I have three more days to Chem MCQs!

Nov 2005 - Q17, Q24
June 2007 - Q12, Q13
Nov 2007 - Q9
June 2006 - Q34
Nov 2006 - Q5
Nov 2009 Variant 12 - Q3
Nov 2008 - Q39
June 2009 - Q29

Can't thank you all enough!

 

[beacon_of_light]

Wow, you're too good! Thanks again.

Alright, I have more questions.. I'll post all of them here and you guys can take your time to respond. I have three more days to Chem MCQs!

Nov 2005 - Q17, Q24
June 2007 - Q12, Q13
Nov 2007 - Q9
June 2006 - Q34
Nov 2006 - Q5
Nov 2009 Variant 12 - Q3
Nov 2008 - Q39
June 2009 - Q29

Can't thank you all enough!

Nov 2005-
q17: ligands not in the syllabus!
q24: now butan-2-ol will form but-1-ene n but-2-ene .......and then but-2-ene will have cis-trans isomerism...rest of the options donot show this!

 

[beacon_of_light]

June07:
q12: NaCl is purely ionic, AlCl3 and SiCl4 are totally covalent...n whats left then???u need to knw these points!
q13:Al completes it outer shell by taking a lone pair of electrons from nitrogen...so taking Al as the central atom...it has 3 hydrogen atoms on one side and N(CH3)3 on the other...in total it makes four bonds ...3 with H and 1 with N...so isn't that tetrahedrally arranged!

 

[beacon_of_light]

Nov 07:
q9: first find moles of sulphite and using equation find moles of electrons lost by S032-..using electrons gained = electrons lost...find the electrons gained by per mole of salt...

 

[beacon_of_light]

june06:
q34: MgCl2 will conduct electricity in liquid state. while SiCl4 n PCl3 are hydrolysed by water producing HCl which then conducts electricity...