Chemistry: Post your doubts here!

[princess Anu]

2-bromo-2-methylpropane

The longest chain has 3 carbons.
The second carbon has a bromine atom and a methyl group attached. Perhaps it's easier to understand if the compound is written like this:
CH3C(CH3)BrCH3

but why are we not taking the functional group ie Br in the longest chain? isn't it a rule to always include the functional group of a compound in the longest chain? but here we're actually taking br as a branch :/ whyy

 

[qwertypoiu]

How do shell/ subshell/ orbital mainly differ from each other??

Shell is the principal quantum number.
It's like the first shell, second shell, third shell we learnt in igs.
Within shells, there are subshells.
So 1s is a subshell, 2p is a subshell, 4f, etc.
Within these subshells are orbitals. Orbitals allow two electrons within themselves, and have different orientations. We need to know that the p subshell can contain up to 6 electrons, because it has 3 orbitals within it, with different orientation:
Px, Py. Pz...
each of these contain 2 electrons, so in total 6 in a p subshell.

 

[qwertypoiu]

but why are we not taking the functional group ie Br in the longest chain? isn't it a rule to always include the functional group of a compound in the longest chain? but here we're actually taking br as a branch :/ whyy

Functional groups are always side chains. We name compounds based on longest carbon chain.

EDIT: IT'S NOT! See below.

 

[Metanoia]

Functional groups are always side chains. We name compounds based on longest carbon chain.

I'll correct this. The longest chain must contain the principal functional group.

http://www.masterorganicchemistry.c...functional-group-priorities-for-nomenclature/

 

[qwertypoiu]

I'll correct this. The longest chain must contain the principal functional group. Halogens are of lower ranking than alkanes, so halogens are considered as prefixes.

http://www.masterorganicchemistry.c...functional-group-priorities-for-nomenclature/

Thank you.

 

[Fiery987]

M/J 2010 P22
Q#5 b (iii)
I wrote Al2O3 as it is found in pumice.
How is the answer only SiO2??

 

[princess Anu]

can we show Hydrogen bonding between hydrazine and ethanol like in blue? the examiner report however doesn't make hydrogen bond between O of alcohol and H on hydrazine..

 

[qwertypoiu]

can we show Hydrogen bonding between hydrazine and ethanol like in blue? the examiner report however doesn't make hydrogen bond between O of alcohol and H on hydrazine..View attachment 52916

The second diagram given shows the hydrogen bond between oxygen atom of the alcohol and the hydrogen atom of hydrazine.

However, I do not think you should make two hydrogen bonds between just two molecules like that. I think it's better to make one, and then there should be another, third molecule, to receive the next hydrogen bonding... If that makes sense...

 

[Xaptor16]

15 Use of the Data Booklet is relevant to this question. The nitrates of beryllium, calcium, magnesium, and strontium all decompose in the same way when heated. When 2.00 g of one of these anhydrous nitrates is decomposed, 1.32 g of gas is produced. What is the nitrate?
A beryllium nitrate
B calcium nitrate
C magnesium nitrate
D strontium nitrate
answer is B... I don't get how to get the answer here.
17 Use of the Data Booklet is relevant to this question. 1.15 g of a metallic element reacts with 300 cm3 of oxygen at 298 K and 1 atm pressure, to form an oxide which contains O2– ions. What could be the identity of the metal?
A calcium
B magnesium
C potassium
D sodium
answer is D, please explain how

 

[nehaoscar]

When calculating bond angles, you have fixed shapes. You calculate those shapes by using the number of bond pairs and lone pairs.
Now when determining shapes, you only use s bonds in bond pairs right? the p bonds are ignored right?

 

[nehaoscar]

For this question, the nitrogen has 3 lone electrons right? - As is uses one electron to form a covalent bond with each of the 2 sulfur's around it.
And Nitrogen originally has 5 valence shell electrons, so if 2 are used in bond pairs, then than leaves 3 lone electrons.
Then how can it just have 1 lone pair? What about the 1 electron left??

 

[DESTROYER1198]

can someone please help. I would really appreciate it if someone can explain for me s12 qp23 Q5)B) i & ii and C)

 

[The Sarcastic Retard]

15 Use of the Data Booklet is relevant to this question. The nitrates of beryllium, calcium, magnesium, and strontium all decompose in the same way when heated. When 2.00 g of one of these anhydrous nitrates is decomposed, 1.32 g of gas is produced. What is the nitrate?
A beryllium nitrate
B calcium nitrate
C magnesium nitrate
D strontium nitrate
answer is B... I don't get how to get the answer here.
17 Use of the Data Booklet is relevant to this question. 1.15 g of a metallic element reacts with 300 cm3 of oxygen at 298 K and 1 atm pressure, to form an oxide which contains O2– ions. What could be the identity of the metal?
A calcium
B magnesium
C potassium
D sodium
answer is D, please explain how

15)
assuming the element as X, the equation will be X(NO3)2---> XO +2 NO2 + 0.5O2
moles of the nitrate equals the mole of the oxide formed
2/(X+ 14*2 +16*6) = (2-1.32)/(X+16)
solve for X and then match the Mr in the periodic table to find the element.

 

[The Sarcastic Retard]

15 Use of the Data Booklet is relevant to this question. The nitrates of beryllium, calcium, magnesium, and strontium all decompose in the same way when heated. When 2.00 g of one of these anhydrous nitrates is decomposed, 1.32 g of gas is produced. What is the nitrate?
A beryllium nitrate
B calcium nitrate
C magnesium nitrate
D strontium nitrate
answer is B... I don't get how to get the answer here.
17 Use of the Data Booklet is relevant to this question. 1.15 g of a metallic element reacts with 300 cm3 of oxygen at 298 K and 1 atm pressure, to form an oxide which contains O2– ions. What could be the identity of the metal?
A calcium
B magnesium
C potassium
D sodium
answer is D, please explain how

17)Find the moles of O2 using n=v/24 (don't forget to convert cm3 to dm3). Then write down the equations for the combustion of all the metals. Calculate the moles of all the metals using n=m/Ar. Then use mole ratios.

 

[The Sarcastic Retard]

View attachment 52917

For this question, the nitrogen has 3 lone electrons right? - As is uses one electron to form a covalent bond with each of the 2 sulfur's around it.
And Nitrogen originally has 5 valence shell electrons, so if 2 are used in bond pairs, then than leaves 3 lone electrons.
Then how can it just have 1 lone pair? What about the 1 electron left??

Free radical.

 

[The Sarcastic Retard]

When calculating bond angles, you have fixed shapes. You calculate those shapes by using the number of bond pairs and lone pairs.
Now when determining shapes, you only use s bonds in bond pairs right? the p bonds are ignored right?

When Sp3 hybridized its angle = 109.5 and shape is tetrahedral, 4BP. (No lone pair)
When Sp2 hybridized it angle = 120 and shape is triogonal planer, 3BP. (No lone pair)
When Sp hybridized it aangle = 180 and shape is linear, 2BP. (No lone pair)
In case of lone pair Angle decreases by some amount.
In case of NH3 and CH4, CH4 has no LP only 4 BP hence 109.5 is angle and tetrahedral is the shape. NH3 has 1 LP and 3 BP so it wont have 109.5 angle slight lesser than that, around 107 and shape is Trigonal pyramidal.

 

[The Sarcastic Retard]

When calculating bond angles, you have fixed shapes. You calculate those shapes by using the number of bond pairs and lone pairs.
Now when determining shapes, you only use s bonds in bond pairs right? the p bonds are ignored right?

Double bond has 1 sigma and 1 pi bond. So ya, sigma bond is always taken into account while u r dealing with hybridizaation or finding BP

 

[The Sarcastic Retard]

Hi everyone, AsSalamoAlaikum Wr Wb..

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah members around will help you.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!

Chemistry Notes:


http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Tips for solving chemistry MCQs 9701/01

Chemistry P5 Tips and Notes

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.


Regards,
XPC Staff.

*Chemistry worksheets Link shared by hassam * Not working. XPFMember

 

[Lola_sweet]

*Chemistry worksheets Link shared by hassam * Not working. XPFMember

they r blocked in my country

 

[The Sarcastic Retard]

they r blocked in my country

I want to see 'em. XPFMember upload PDFs here, please?