Chem doubts

[nid404]

Oh & Thanks Mani

[sweetie]

oh, am sorry its Q11> not 9

thanx

[nid404]

Q11) Ans is B.
Le chatelier's  principle....
When u add more H2O2, it takes longer for the breakdown since the amount of catalyst may not be sufficient...more H2O2 and hence more vol of O2 produced

[sweetie]

Thank You sooooooooooooo much

[sweetie]

i have doubts tooo 

nov.06
Q40> Why is no.3 wrong? isnt c-o double bond a ketone?
Q37> PLZ XPLAIN
Q21>  PLZ XPLAIN
Q14, Q11, Q6, Q9

THANX IN ADVANCE 
                                     

cud u plzzz help me in these Que's toooo???

[MaNi_DaDuDe]

Oh & Thanks Mani

You're welcome.

Well deserved.

[Phosu]

1) jun 09 pp1 q40

2) a 2g sample of hydrogen at temperature T and volume V exerts a presssure P. Deuterium ₁H², is an isotope of hydrogen. which of the following would also exert a pressure P at the same temperature T?
a) 2g of deuterium of volume V
b) 4g of deuterium of volume V/2
c) a mixture of 1g of hydrogen and 2g of deuterium of total volume V
d) a mixture of 2g of hydrogen and 1g of deuterium of total volume 2V

3) Which property applies to halogens as group VII is descended?
a)Hydrogen-halogen bond energy decreases
b) intermolecular forces between the elements decrease
c) ions become less strongly reducing
d) thermal stability of the hydrides increases.

[vanibharutham]

Im doing Edexcel Chem
so i cant help with question 2,

but question 3, the answer is A

a) H-F has the strongest bond enthalpy while H-I has the lowest bond enthalpy because F is more electronegative and it is hard to break the bond
b) Intermolecular forces increase down the group because the size of the atom increases so more chance of an instantaneous dipole-induced dipole because there are more electrons
c) OILRIG - oxidation is loss of electron, reduction is gain.... but here we are considering Reducing Power, or how easily they are oxidised....as mentioned earlier.... Flourine is the most electronegative...so it is most difficult to remove electrons from it... so ions become more strongly reducing.
d) Same explanation as bond enthalpy...

[sweetie]

Q9 nd 25 of da first 2 papers ( specimen 01)

Q21 and 26 of  next 2 sheets ( may 01)

thats all !!!
plz reply ASAP

[nid404]

9) Cl₂(g)----> Cl(g) + Cl(g)
atomisation energy...+244kj/mol
Cl(g)--->2Cl- -364 kj/mol

I think the answer should be A

25) A,B and D are incorrect... cuz it's possible to have a gas of this composition, it may be immiscible in water and it can have a mass less than 32...consider HCHO...mass 30
So, C

21)stoichio...
unsaturates...alkenes have formula Cn H2n in this hydrocarbon, there r 10 less hydrogen atoms...5 H2
so 4.1g~0.01 moles of the hydrocarbon will react with 0.05 moles of H2
0.05 moles of H2= 0.05 X2 grams=0.1g
no option? 
C is 0.12g and it will react completely with squalene...so C i guess

26) B it's a tertiary alcohol...won't undergo oxidation

[sweetie]

 Thank You

for Q9 the ms says  C ( dunno why)

da rest of da que's r ok,   but can u tell me  in Q21 why dont we react the alkene with 6H2 , to compensate for the 10 and 2 more atoms to break the double bond

[tmisterr]

For question 9, first the Cl₂ molecule breaks and the enthalpy change from the data booklet is +244. then you have two Cl atoms. definition of electron affinity is the enthalpy change when one mole of gaseous atoms each gain an electron to have a single negative charge. so since there are two, they will form two Cl^-. enthalpy change for one mole is -364 but since there are two, it will be -728, but remember +244 was used in the beginning to to break the Cl-Cl bond so -728+244= -484

for question 26, I believe the answer is A, because A contains a aldehyde group and it can be oxidised further into a carboxylic acid which will change the coLour from orange to green. This can not be done with the compound in the question because it contains a tertiary alcohol and a ketone and both cannot be oxidised further so the colour will remain orange.  I do not believe it is B because B has a tertiary alcohol which cannot be oxidised further so again the colour will remain green.

for question 21,
it is a weird question but this is how i did it. Since it is unsaturated, one of the reactions alkenes undergo is hydrogenation to form alkanes in the presence of platinum catalyst, which are the conditions stated in the question. so if C₃₀H₅₀ undergoes full hydrogenation, it will become an alkane C₃₀H₆₂ so u need to a add 12 moles of hydrogen atoms so (4.1/410)*12= 0.12 which is C.

[sweetie]

Thank You sooo much  

and ya ur ans. for q26 is riteee , i checked the ms

cud u also help me with Q21 of 5th sheet ( nov01)
and Q31 and 32 of last sheet ( nov01)

[tmisterr]

q 21, I should be D. A would be formed since it is a reducing atmosphere, reduction is the addition of hydrogen so ethene can be reduced to ethane. B can also be form when methane reacts with ammonia to form methyl-amine. ethanol, C ,can also be formed when ethene reacts with water (steam) the high energy can convert water to steam. D is an acid, which are you usually formed by oxidation reactions, so it can't be formed here.

q 31 D again. the most abundant is the second bar. one sulphur atom has a mass of 32.1 so the second bar must be 2 sulphur atoms S₂ since its mass is 64.2, making 1 correct. for 2 there is no way to come to this conclusion. and 3, they are not different isotopes they are just different molecules of sulphur with different number of atoms in each molecule.

q32 I should be A. as you know temperature is the measure of kinetic energy in a substance so even though there be some at very high kinetic energy and some with a very low kinetic energy(think of Boltzmann distribution curve), since they are at a constant temperature, the average kinetic energy should be the same. 2 is true also since in 1 dm³ they have the same number of moles and since P has an Mr which is four time greater it is 4 times heavier. 3 is also true, same number of molecules of each gas because of same number of moles so they contribute equal pressure.

Can you do me a favour and send me these two papers (specimen 01 and oct/nov 01)? I can't find them on xtreme papers or FEP and they seem like they would be good practice.

[sweetie]

q 21, I should be D. A would be formed since it is a reducing atmosphere, reduction is the addition of hydrogen so ethene can be reduced to ethane. B can also be form when methane reacts with ammonia to form methyl-amine. ethanol, C ,can also be formed when ethene reacts with water (steam) the high energy can convert water to steam. D is an acid, which are you usually formed by oxidation reactions, so it can't be formed here.

q 31 D again. the most abundant is the second bar. one sulphur atom has a mass of 32.1 so the second bar must be 2 sulphur atoms S₂ since its mass is 64.2, making 1 correct. for 2 there is no way to come to this conclusion. and 3, they are not different isotopes they are just different molecules of sulphur with different number of atoms in each molecule.

q32 I should be A. as you know temperature is the measure of kinetic energy in a substance so even though there be some at very high kinetic energy and some with a very low kinetic energy(think of Boltzmann distribution curve), since they are at a constant temperature, the average kinetic energy should be the same. 2 is true also since in 1 dm³ they have the same number of moles and since P has an Mr which is four time greater it is 4 times heavier. 3 is also true, same number of molecules of each gas because of same number of moles so they contribute equal pressure.

Can you do me a favour and send me these two papers (specimen 01 and oct/nov 01)? I can't find them on xtreme papers or FEP and they seem like they would be good practice.

ya, sure ill sent them as soon as i scan dem 4 u

nd 4 Q 31, how do we know if the bars represent isotopes or atoms ??
6 The density of ice is 1.00 g cm–3.

cud u also xplain this Q ......

Q>What is the volume of steam produced when 1.00 cm3 of ice is heated to 323 °C (596 K) at a
pressure of one atmosphere (101 kPa)?

[1 mol of a gas occupies 24.0 dm3 at 25 °C (298 K) and one atmosphere.]
A. 0.267 dm3  B. 1.33 dm3  C. 2.67 dm3   D. 48.0 dm3


thanx sooo much for da help, By the way all ur answers r riteeee!!!