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Chemistry: Post your doubts here!

Xaptor16

Xaptor16

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shazmina said:
Screenshot_19.jpg

The answer for this question is A
Can someone please explain me how compound A shows Methyl Methyl Propenoate ////
Click to expand...
I asked my teacher the same question and this is how she explained it to me:
She told me 1) draw propene (keep in mind that the question is talking about Propenoate not propanoate. There's a difference.)
2) make it propenoic acid
3) make an ester with methanol
4) now add a Methyl group to the compound.
You'll see that A is the only possible option
I know that's not very good explanation but I hope you get it :D
 
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shazmina

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Xaptor16 said:
I asked my teacher the same question and this is how she explained it to me:
She told me 1) draw propene (keep in mind that the question is talking about Propenoate not propanoate. There's a difference.)
2) make it propenoic acid
3) make an ester with methanol
4) now add a Methyl group to the compound.
You'll see that A is the only possible option
I know that's not very good explanation but I hope you get it :D
Click to expand...
Wooow i got it ... Thank you so much :D MAy god bless you :)
 
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iYuuki

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Hey guys, can anyone please help me out with these 2 questions?
For the file "Chem2" i need help with 2 (ii) & (iv). Thank you! :)
 

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qwertypoiu

qwertypoiu

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shazmina said:
http://onlineexamhelp.com/wp-content/uploads/2014/08/9701_s14_qp_11.pdf Question 29 of this paper ...
Can anyone please draw and show me all the possible Geometrical isomers that exist for that compound ....
Click to expand...
There are four geometrical isomers. Remember that there are TWO double bonds in the structure, and both are able to have geometrical isomerism. It is difficult to draw them, but imagine this:

FIRST DOUBLE BOND...........SECOND DOUBLE BOND.......
1). cis..........................................cis.................
2). cis........................................trans.................
3). trans......................................cis...........................
4). trans....................................trans...........................


Therefore, there are 4 isomers. In general, if there are x double bonds in a compound that are able to show cis-trans isomerism, there are 2^x geometric isomers of the compound. (eg if there are 3 double bonds, 8 isomers will be seen.)


EDIT: Sorry, it should be three, as cis,trans and trans,cis will be the same, just flipped around; due to this compound's symmetry.
 
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Metanoia

Metanoia

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qwertypoiu said:
There are four geometrical isomers. Remember that there are TWO double bonds in the structure, and both are able to have geometrical isomerism. It is difficult to draw them, but imagine this:

FIRST DOUBLE BOND...........SECOND DOUBLE BOND.......
1). cis..........................................cis.................
2). cis........................................trans.................
3). trans......................................cis...........................
4). trans....................................trans...........................


Therefore, there are 4 isomers. In general, if there are x double bonds in a compound that are able to show cis-trans isomerism, there are 2^x geometric isomers of the compound. (eg if there are 3 double bonds, 8 isomers will be seen.)
Click to expand...
You need to subtract 1 isomer in this question as its a symmetrical molecule. The cis-trans and trans- cis are identical.
 
Metanoia

Metanoia

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My Name said:
upload_2015-3-28_17-15-22-png.51487

Answer is C
Click to expand...
The cold dilute KMnO4 adds 2 OH across the C=C bonds, the original OH on the bottom not oxidised to a ketone as it is not heated. So there will be 3 OH in the product.

The hot KMnO4 cleaves the C=C bonds, you have only the bottom and 3rd from bottom rings with 6 carbons.
 
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shazmina

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qwertypoiu said:
There are four geometrical isomers. Remember that there are TWO double bonds in the structure, and both are able to have geometrical isomerism. It is difficult to draw them, but imagine this:

FIRST DOUBLE BOND...........SECOND DOUBLE BOND.......
1). cis..........................................cis.................
2). cis........................................trans.................
3). trans......................................cis...........................
4). trans....................................trans...........................


Therefore, there are 4 isomers. In general, if there are x double bonds in a compound that are able to show cis-trans isomerism, there are 2^x geometric isomers of the compound. (eg if there are 3 double bonds, 8 isomers will be seen.)


EDIT: Sorry, it should be three, as cis,trans and trans,cis will be the same, just flipped around; due to this compound's symmetry.
Click to expand...
Thanks alot brother :D Very comprehensible :)
 
A

Ahmed Aqdam

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The Sarcastic Retard said:
http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_12.pdf
Q4
Q6
Q15
Q16
Q17
Q30 to Q36
Click to expand...
4. PV/T is equal before and after the valve is opened.
Temperature is taken in Kelvins. Volume is taken at V before valve is opened. Total volume after is 4V after valve is opened.
1*10^5*V/(20+273)=P*(4V)/(100+273)
Solve to get 3.18*10^4.

6. Al4C3+NaOH+H2O----->NaAlO2+hydrocarbon
Al has 4 atoms so there are 4 moles of NaAlO2 to balance the equation and hence 4 moles of NaOH too. Now there are 8 oxygen atoms in products but only 4 in reactants so 4 more are needed from H2O to balance. This makes 3 C atoms and 12 H atoms. Only CH4 has 4 times Hydrogen atoms as Carbon does.
Al4C3+4NaOH+4H2O----->4NaAlO2+3CH4

15. K2O+H2SO4 so both react in 1:1 ratio.
Moles of H2SO4: 2*15/1000=0.03
Moles of K2O in 250 cm^3=0.03*250/25=0.3
Mr of K2O=94.2
Mass=94.2*0.3=28.3g

16. In cold NaClO is produced. Na is +1, O is -2 so Cl must be +1.
In hot NaClO3 is produced. Na is +1, O is -6 when added so Cl is +5.
NaCl is also produced in both reactions and Cl is -1 in this.

17. Br2 will not react with Cl- as it is less reactive.
Cl2 will displace Br-. This will be oxidation as Br will become 0 from -1.
 
Xylferion

Xylferion

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Ahmed Aqdam said:
4. PV/T is equal before and after the valve is opened.
Temperature is taken in Kelvins. Volume is taken at V before valve is opened. Total volume after is 4V after valve is opened.
1*10^5*V/(20+273)=P*(4V)/(100+273)
Solve to get 3.18*10^4.

6. Al4C3+NaOH+H2O----->NaAlO2+hydrocarbon
Al has 4 atoms so there are 4 moles of NaAlO2 to balance the equation and hence 4 moles of NaOH too. Now there are 8 oxygen atoms in products but only 4 in reactants so 4 more are needed from H2O to balance. This makes 3 C atoms and 12 H atoms. Only CH4 has 4 times Hydrogen atoms as Carbon does.
Al4C3+4NaOH+4H2O----->4NaAlO2+3CH4

15. K2O+H2SO4 so both react in 1:1 ratio.
Moles of H2SO4: 2*15/1000=0.03
Moles of K2O in 250 cm^3=0.03*250/25=0.3
Mr of K2O=94.2
Mass=94.2*0.3=28.3g

16. In cold NaClO is produced. Na is +1, O is -2 so Cl must be +1.
In hot NaClO3 is produced. Na is +1, O is -6 when added so Cl is +5.
NaCl is also produced in both reactions and Cl is -1 in this.

17. Br2 will not react with Cl- as it is less reactive.
Cl2 will displace Br-. This will be oxidation as Br will become 0 from -1.
Click to expand...

For 15, how do you figure out the ratio? How did you know it's 1:1? o_O
 
qwertypoiu

qwertypoiu

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Xylferion said:
For 15, how do you figure out the ratio? How did you know it's 1:1? o_O
Click to expand...
Try writing the full equation and balancing it. Metal oxides react with acids to form a salt and water:
K2O + H2SO4 ---> K2SO4 + H2O.
This equation needs no balancing, and you can see therefore that the ratio of all the species is 1:1:1:1
 
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