Qualification > Sciences
Chem doubts
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 :D
and ya ur ans. for q26 is riteee , i checked the ms ;D
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:
--- Quote from: tmisterr on April 15, 2010, 08:07:54 am ---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.
--- End quote ---
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!!!
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