Chemistry: Post your doubts here!

[♣♠ Magnanimous ♣♠]

Cracking of octene produces molecules that have less carbons than octene.

W, X, Y and Z are thus all possible products of cracking of octene.

But on addition of those should form OCTENE na?
Is thermal cracking and catalytic cracking different?

 

[Metanoia]

But on addition of those should form OCTENE na?
Is thermal cracking and catalytic cracking different?

Adding them does not necessary give us octene, cause there might be other products that are not listed.

If we stick to the thinking that these are the only products, it is still possible.

Just balance the equation
aC4H8 --> bC2H4 + cC3H6 + dC3H8 + eC4H6

The mistake made is that you wrongly viewed that there is only one C4H8 involved in the cracking.

 

[♣♠ Magnanimous ♣♠]

Adding them does not necessary give us octene, cause there might be other products that are not listed.

If we stick to the thinking that these are the only products, it is still possible.

Just balance the equation
aC4H8 --> bC2H4 + cC3H6 + dC3H8 + eC4H6

The mistake made is that you wrongly viewed that there is only one C4H8 involved in the cracking.

Wo wo
Thanks

 

[princess Anu]

.

 

[princess Anu]

how is 2 redox?

 

[Metanoia]

.

Cl and O are similar in electronegativity and cancels each other out to an extent.

how is 2 redox?

Free radical substitution.

By keeping track of the Br, you can see that the Br is reduced (oxidation state decreased form 0 to -1)

Br2 --> HBr

 

[princess Anu]

Cl and O are similar in electronegativity and cancels each other out to an extent.



Free radical substitution.

By keeping track of the Br, you can see that the Br is reduced (oxidation state decreased form 0 to -1)

Br2 --> HBr

yeah but where is oxidation

 

[Metanoia]

yeah but where is oxidation

The carbon (in the alkane) that had its H replaced by Br is oxidized.

 

[Boss201]

question number 4

Ans : B

am unable to calculate it

if you could please show the working

Thanks for your help .

 

[Tasneem_m98]

Someone please help. M/J 2014 paper 11 number 1
I have trouble in such questions unfortunately..

Atoms of the element X have six unpaired electrons.
What could be element X?
A carbon
B chromium
C iron
D selenium

Correct answer is B chromium

Thank you in advance !

 

[qwertypoiu]

Someone please help. M/J 2014 paper 11 number 1
I have trouble in such questions unfortunately..

Atoms of the element X have six unpaired electrons.
What could be element X?
A carbon
B chromium
C iron
D selenium

Correct answer is B chromium

Thank you in advance !

Electronic configuration of chromium is:

[Ar] 3d5 4s1

As you can see it has 6 unpaired electrons.

 

[Tasneem_m98]

Electronic configuration of chromium is:

[Ar] 3d5 4s1

As you can see it has 6 unpaired electrons.

Oh yeah okay thank you so much! Jazak Allah kheir!

 

[qwertypoiu]

question number 4

Ans : B

am unable to calculate it

if you could please show the working

Thanks for your help .

Reactant bond energies - Product bond energies.

Reactant bond energies = (C≡O) + 2(H-H) = 1077 + 2*436 = 1949
Product bond energies = 3(C-H) + (C-O) + (O-H) = 3*410 + 360 + 460 = 2050

Reactant bond energies - Product bond energies = 1949 - 2050 = -101

 

[Tasneem_m98]

Someone please help. M/J 2014 paper 11 number 8
Link:https://www.google.com.sa/url?sa=t&...EQFjAD&usg=AFQjCNGId_JPSUXCASA68wmpsYeS_rC1Xg

Thank you!

 

[Boss201]

Reactant bond energies - Product bond energies.

Reactant bond energies = (C≡O) + 2(H-H) = 1077 + 2*436 = 1949
Product bond energies = 3(C-H) + (C-O) + (O-H) = 3*410 + 360 + 460 = 2050

Reactant bond energies - Product bond energies = 1949 - 2050 = -101

From the given equation how does (C-O) bond(CH3OH) get included ? in the product bond energies

And how come its not 4(H-H) bond in reactant energies as it the equation gave 2H2

 

[ashcull14]

 

[ashcull14]

 

[qwertypoiu]

View attachment 54037

D?
Cuz C-I bond is the weakest so will produce precipitate fastest

 

[qwertypoiu]

View attachment 54035

A?
Cuz it contains the most C-Cl bonds, so will produce the most amount of Cl• free radicals

 

[qwertypoiu]

From the given equation how does (C-O) bond(CH3OH) get included ? in the product bond energies

And how come its not 4(H-H) bond in reactant energies as it the equation gave 2H2

H2 is made of two hydrogen atoms bonded together. Like this:
H-H. As you can see there is only one bond. There is two bonds therefore in two H2 molecules:
H-H
H-H

Note that the dash between them represents the bond.

Look at methanol:

Now you can see it has a C-O bond.