Chemistry MCQ thread...

[Saturation]

june 2002 Q21 and Q39 plxxx???

Q21, HELP!

Q 39: It's nucleophillic addition, since halogenoalkane is being hydrolyzed to alcohol, so 1 is right. X to Z does represent the activation energy, so 3 is right, which means that 2 has to be right aswell, so it's A.

(I'm guessing that since the C-Hal bond is breaking, so as it's length increases, the bond gets weaker and is eventually broken! :Search: )

 

[Mssamgirl15]

Thanks for answering my question, Saturation.

Another question,someone,please.
MAY/JUNE 2009. QUESTION 31.

On a scale in which the mass of a 12C atom is 12 the relative molecular mass of a particular
sample of chlorine is 72.
Which properties of the atoms in this sample are always the same?
1 radius
2 nucleon number
3 isotopic mass

 

[Abdulrab]

http://www.xtremepapers.me/CIE/Internat ... 9_qp_1.pdf
please solve Q 6, 8, 12, 15, 16, 18 ,19, 20, 24,25, 26, 30, 38

please answer them with full explanaton !!! thanks

 

[Xthegreat]

6 - A. bromoethane has a bond angle of 109' whereas the product ethene has a bond angle of 120'
B. methane has a bond angle of 109' whereas CO2 is 180'
C. methane and chloromethane both has 109
D. ethene is 120' and ethane is 109
so it's D

 

[Hateexams93]

why is the answer B ?? though the bond energy of A is higher !

B, that's why alkanes are the most useful fuels. Plus make balanced equations for combustion of each of 1 mole of them. The equation in which total number of moles of Co2 and H2O combined will be greater is B.

i'm getting the same number of moles for A and B :/
And the bond energy of A i higher -.- how do we know which one will give the highest ?

 

[Xthegreat]

18
- my lecturer say that the only alkaline gas we know is AS level is NH3. so just memorise that.
- as for the solid residue, sodium salts are all colourless, Fe2+ salts are green. you have to memorise this too.

 

[Xthegreat]

24
- the hydrolysis of bromoethane is to replace the -Br group with an -OH group
- the -OH group is negatively charged.
- negatively charge molecules like postively-charged region
- nucleus are positively-charged, hence molecules/atoms that like positively-charged regions are called NUCLEOPHILE
- so after the -OH group goes in, -Br which is also negatively-charged is produced.
- hence both group are NUECLEOPHILES.

 

[hassam]

Which one of the following statements is correct?
A HI has a higher boiling point than HCl because HI has stronger hydrogen bonding.
B PCl5 is hydrolysed by water to form a weakly acidic solution.
C The reducing ability of the halide ions increases as the size of the anion increases.
D The solubility of the Group II hydroxides decreases as the size of the cation increases.

 

[Zishi]

Which one of the following statements is correct?
A HI has a higher boiling point than HCl because HI has stronger hydrogen bonding.
B PCl5 is hydrolysed by water to form a weakly acidic solution.
C The reducing ability of the halide ions increases as the size of the anion increases.
D The solubility of the Group II hydroxides decreases as the size of the cation increases.

C

 

[Zishi]

Thanks for answering my question, Saturation.

Another question,someone,please.
MAY/JUNE 2009. QUESTION 31.

On a scale in which the mass of a 12C atom is 12 the relative molecular mass of a particular
sample of chlorine is 72.
Which properties of the atoms in this sample are always the same?
1 radius
2 nucleon number
3 isotopic mass

D, because Isotopes have different number of nucleons and so different isotopic masses. So only 1st option is correct.

 

[Zishi]

why is the answer B ?? though the bond energy of A is higher !

B, that's why alkanes are the most useful fuels. Plus make balanced equations for combustion of each of 1 mole of them. The equation in which total number of moles of Co2 and H2O combined will be greater is B.

i'm getting the same number of moles for A and B :/
And the bond energy of A i higher -.- how do we know which one will give the highest ?

Post the question again so that I may make the number of moles myself...

NOV 02 Q8 AND Q9
??
CAN ANY 1 ?

See the attachment.

 

[Hateexams93]

viewtopic.php?f=26&t=8584&start=490
THe question is on this page ,about combustion

 

[Zishi]

why is the answer B ?? though the bond energy of A is higher !

Ok, so the case is that in burning of A, 4.5 moles of O2 are used, but in burning of B(alkane), 5 moles of O2 are used. Thios extra 0.5 mole of O2 outweighs the effect of "higher bond energy of O-H than C-H bonds). You may calculate the delta H using the values from data booklet. That will help you to understand it.

 

[ninjas4life]

why is it all of them?

 

[Xthegreat]

1 - when the substance is in water, the -ONa part will become, -O- and Na+
2 - alkane and alkenes are from crude oil, of course they dissolve in oil
3 - all C are bonded to 4 group hence they are all tetrahedral

 

[Saturation]

How do you do number 7!? (please show full working!)

http://www.xtremepapers.me/CIE/Internat ... 5_qp_1.pdf

Anyone? :good:

 

[Saturation]

why is it all of them?

1 is probably because since this is ionic, when you put it in water it splits up in Na+ and RO- , which attracts the water molecules (hydrated ions).

 

[xsilver]

2002 oct / nov paper 1
Q16 pls

 

[hassam]

 

[Zishi]

How do you do number 7!? (please show full working!)

http://www.xtremepapers.me/CIE/Internat ... 5_qp_1.pdf

Anyone? :good:

Is it C? -81