AS Chemistry P2 Prep.

[Muhammad Ahmer Ali]

wats the bond angle and shape of a compound with 2 bond pairs and 1 lone pair

I just found it out in my notes 2bond pair+1 lone pairs is 117.5 with an ALMOST PLANER shape

 

[Saad (سعد)]

wats the bond angle and shape of a compound with 2 bond pairs and 1 lone pair

2 bonds, 0 lone pair = Linear, 180 degrees, ex: CO2
2 bonds, 1 lone pair = Angular/Bent, 117 degrees, ex: SO2
2 bonds, 2 lone pair = Angular/Bent, 104.5 degrees, ex: H2O.
3 bonds, 0 lone pair = Trigonal Planar, 120 degrees, ex: AlCl3 or BF3
3 bonds, 1 lone pair = Trigonal Pyramidal, 107 degrees, ex: NH3
4 bonds, 0 lone pair = tetrahedral, 109.5 degrees, ex: CH4
5 bonds, 0 lone pair = trigonal bypyramidal, 90/120 degrees, ex: PCl5
6 bonds, 0 lone pair = Octahedral, and 90 degrees, ex: SF6.

 

[littlecloud11]

fromwhere this angle came?lol no ...according to me its either 12's 1170 or 117 but not sure which1?

It 117.5 the molecule will have a bent shape so the bond angle has to be a little smaller than 120.

 

[angelgirl:)]

I just found it out in my notes 2bond pair+1 lone pairs is 117.5 with an ALMOST PLANER shape

yes dats correct....

 

[angelgirl:)]

It 117.5 the molecule will have a bent shape so the bond angle has to be a little smaller than 120.

thats y i was confucsed ..the bond angle has to be in b/w 120 and 117..

 

[alim]

it cant be 120 cause its for trigonal planar(3 bond pairs)....... it must be 117 then b/c a lone pair

 

[alim]

thanx every1

 

[angelgirl:)]

It 117.5 the molecule will have a bent shape so the bond angle has to be a little smaller than 120.

u have changed my post...

 

[littlecloud11]

thats y i was confucsed ..the bond angle has to be in b/w 120 and 117..

yupp. an angle of 120 would give it a trigonal planar shape.

 

[Muhammad Ahmer Ali]

Now, someone, please kindly, riddle me this.

Question 4, (f), (iii):

Paper: Click Me
Mark Scheme: No, Me!!!

... Why on planet Earth do those carbon atoms (in the mark scheme answer) have five bonds each?

They have 3 bonds each where do you see 5?

 

[angelgirl:)]

yupp. an angle of 120 would give it a trigonal planar shape.

since it has 3 bond pairs...but among them 1 lone pair and 2 bond pair ...the angle has to be in b/w 120 and 117...dats wat my teacher told me ..

 

[Muhammad Ahmer Ali]

They have 3 bonds each where do you see 5?

If you are asking about the double bonds then it is misprinting

 

[Saad (سعد)]

They have 3 bonds each where do you see 5?

Look again. The C on the right has 2 bonds with the C on the left, 1 bond with Br, 1 with CH2Br and 1 with H. That's 5 bonds total.

The C on the left has 2 bonds with the C on the right, 1 bond with H, 1 with CH3 and 1 with the R-side chain. That's also 5 bonds total.

So each Carbon atom has 5 bonds.

There are two explanations for that; I'm missing something VERY big, OR, the Examiner had a spat with his wife the morning before making the Mark Scheme.

 

[Muhammad Ahmer Ali]

Look again. The C on the right has 2 bonds with the C on the left, 1 bond with Br, 1 with CH2Br and 1 with H. That's 5 bonds total.

The C on the left has 2 bonds with the C on the right, 1 bond with H, 1 with CH3 and 1 with the R-side chain. That's also 5 bonds total.

So each Carbon atom has 5 bonds.

There are two explanations for that; I'm missing something VERY big, OR, the Examiner had a spat with his wife the morning before making the Mark Scheme.

Its mis printing for double bond

 

[Saad (سعد)]

If you are asking about the double bonds then it is misprinting

CIE standards are falling... Anyways, so what's the real shape?

 

[Muhammad Ahmer Ali]

CIE standards are falling... Anyways, so what's the real shape?

Its the same with a single bond b/w Carbon atoms

 

[Saad (سعد)]

Its the same with a single bond b/w Carbon atoms

Jazak Allah Khayr.

Can someone please explain to me the reactions of KMnO4 on Alkenes?

Also, why does only KMnO4 show that kind of reaction with Alkenes; why doesn't K2Cr2O7, as they're both oxidizing agents?

 

[angelgirl:)]

ok have 1 doubt..
all grpI MNO3 decompose to MNO2 + O2
but Li haas high polarising power so it decompose like grpII M(NO3)2............... LNO3 ---->MO2 +NO2 or MO2 +NO2 +O2 as well...?
do Li on decomposition releases O2 or not ? dats my doubt...

 

[Muhammad Ahmer Ali]

Jazak Allah Khayr.

Can someone please explain to me the reactions of KMnO4 on Alkenes?

If the end of the molecule contains CH2 then CH2 is converted into H20 and CO2. The other side of the molecule must contain 2 bond, i.e CH and an other R group. The CH molecule is always converted into COOH. For eg, CH3-CH=CH2 = CH3COOH+CO2+H20.
Furhtermore there is a possibltiy that the left side of the molecule contains 2 R gps other than CH, if this happens then the resulting molecule is R-C-R with a double bond ketone oxygen group above oxygen. For e.g (CH3)2=CH2 = CH3_C(=O)-CH3+ Co2 + H2O

 

[Muhammad Ahmer Ali]

Jazak Allah Khayr.

Can someone please explain to me the reactions of KMnO4 on Alkenes?

Also, why does only KMnO4 show that kind of reaction with Alkenes; why doesn't K2Cr2O7, as they're both oxidizing agents?

Regarding K2Cr2O7 this is a weak oxidising agent where Kmno4 is a strong oxidising agents so K2cr2O7 is only able to oxidise to OH, where Kmno4 furhter oxidises to ketone or CooH