chem mcq...

[sweetiepie]

yeah bt how wil we calculate plz telme m really weak in chemistry ...

 

[xHazeMx]

N2O4 has 0.02 moles which is given in the question. NaOH will have twice that moles as u see (2) beside the NaOH in the equation so ( 2 x 0.02 = 0.04 ) this is for the moles part ( n )
the concentration is already given in the question which is 0.5. now use the formula ( C= n/v ) .. ( C is the concentration and n is the number of moles ) .. put each value in the equation and find volume u will get it 0.08 dm^3 which is the same as 80 cm^3

did u get that ?

 

[sweetiepie]

yeah i calculated so i got it thank u.....

now explain me q.8 of same m/j 2006????

 

[xHazeMx]

yeah i calculated so i got it thank u.....

now explain me q.8 of same m/j 2006????

u welcome
sorry i have to go now. i will help u with more questions later

 

[sweetiepie]

no prb...

 

[sweetiepie]

is there any1 esle to explain me????

 

[hassam]

wat?>

 

[MHHaider707]

Answer is A!!

Transformation from X to Y Enthalpy change is positive that means, Y has got higher energy content than X

now transformation from Y to Z enthalpy change is negative which means, Z has got less energy content than Y, which is best represented by option A!!!

In such questions in which we have to show energy profile diagram of two reactions, there are always two peaks in the diagram!!!
So answer is A....

got it???

 

[sweetiepie]

yeah thank u...

 

[hassam]

39 Which compounds are able to react with concentrated sulphuric acid to give a product that will
decolourise acidic potassium manganate(VII)?
1 (CH3)3COH
2 CH3CH2CH(OH)CH3
3 CH3CO2H

cn any body tell me wats reaction of conc. sulfuric acid with carboxylic acid

 

[MHHaider707]

yeah thank u...

no problem

 

[sheikfathiu]

i think it its 1 2 3

 

[alisha]

39 Which compounds are able to react with concentrated sulphuric acid to give a product that will
decolourise acidic potassium manganate(VII)?
1 (CH3)3COH
2 CH3CH2CH(OH)CH3
3 CH3CO2H

cn any body tell me wats reaction of conc. sulfuric acid with carboxylic acid

I think its only 1 and 2. they are both alcohols and conc. H2SO4 is a dehydrating agent, so if a water molecule is removed you will get alkenes. Alkenes will decolourize potassium manganate because they can get oxidized to ketones/aldehydes/ carboxylic acids depending on the conditions. But 3 is an ester and it will get hydrolyzed by dilute H2SO4 and not conc.

In the presence of H2SO4 (conc) carboxylic acids will react with alcohols to form esters, other than that i dont know.

 

[Hateexams93]

12 Which chlorine compound has bonding that can be described as ionic with some covalent
character?
A NaCl B MgCl2 C AlCl3 D SiCl4
WHY ITS B ?

 

[sniper7137]

39 Which compounds are able to react with concentrated sulphuric acid to give a product that will
decolourise acidic potassium manganate(VII)?
1 (CH3)3COH
2 CH3CH2CH(OH)CH3
3 CH3CO2H

cn any body tell me wats reaction of conc. sulfuric acid with carboxylic acid

I think its only 1 and 2. they are both alcohols and conc. H2SO4 is a dehydrating agent, so if a water molecule is removed you will get alkenes. Alkenes will decolourize potassium manganate because they can get oxidized to ketones/aldehydes/ carboxylic acids depending on the conditions. But 3 is an ester and it will get hydrolyzed by dilute H2SO4 and not conc.

In the presence of H2SO4 (conc) carboxylic acids will react with alcohols to form esters, other than that i dont know.

I think the question is talking about the formation of alkenes from alcohols in the presence of H2SO4. I think it is A and B only are correct as alcohols >> alkenes >> aldehydes / ketones due to cleavage of double bond.

 

[alisha]

12 Which chlorine compound has bonding that can be described as ionic with some covalent
character?
A NaCl B MgCl2 C AlCl3 D SiCl4
WHY ITS B ?

NaCl is entirely ionic, MgCl2 is ionic with some degree of covalency, AlCl3 is ionic with a great degree of covalency (due to dative bond and all) SiCl4 is covalent. this should be remembered. it is in periodicity.

 

[ambitious1]

Hey all,
Can someone please state the answer for Q.11, and explain why is it so?
Thanks! =)

 

[alisha]

wich paper?

 

[ambitious1]

It's the first question posted in the forum, page 1.

 

[alisha]

i think it is B becoz initially the reaction is uncatalyzed and proceeds normally, but as products are formed and one of the product is a catalyst, the rate of reaction is increased so the line gets steeper. They say the answer is c because the product is used up so the rate of reaction decreases, but isnt the rate of reaction actually a measure of how fast the reactants are converted to products? whether the product remains or not is not a problem.