Edexcel CHEMISTRY DOUBTS!!!!

[elemis]

Ahh k , thanks mate

No worries. If possible, please check those answers with your teacher.

[The Golden Girl =D]

No worries. If possible, please check those answers with your teacher.

I'll try iA

[Deadly_king]

I take down notes while my teacher is speaking and this is what I have, some of it just doesn't make sense to me, can someone please go through them and correct me if I am wrong?

It's from the topic Atomic Structure [Unit 1]

1. The p orbital will have less energy compared to the s orbital because s is more stable.

2. p6 has more energy compared to p5 and p3 has more energy compared to p2 because p6 and p3 are more stable compared to p2 and p3.

3. As the distance from the nucleus increases, the energy of the shell increases as it is further apart, so there is less attraction of the electrons by the nucleus and hence it is less stable.

& my fourth question is how do you draw the energy level diagram for lets say Magnesium?
Use this symbol [] to represent the 2 opposite arrows.

Thank you!

I think this will help you.

If you still have any doubts, feel free to ask.

[**RoRo**]

I think this will help you.

If you still have any doubts, feel free to ask.

Thanks a lot!

One more question: why does HBr have a higher boiling point that HCl?
Shouldn't it be the opposite? :/

[Amelia]

In case of HBr and HCl, the most dominant intermolecular forces in them are dispersion forces. Dispersion forces greatly depend on the size of the molecule. i.e. bigger the molecule --> more the number of bonds --> higher the energy require to break the bond for vaporization --> consequently, higher the boiling point. If u look at the periodic table, you will find Br in the row lower than Cl meaning Br atom is bigger than Cl ( note: the size of atom or atomic radius increases as you go down the periodic table). That's why HBr has greater boiling point than HCl.

You are welcome.

[**RoRo**]

In case of HBr and HCl, the most dominant intermolecular forces in them are dispersion forces. Dispersion forces greatly depend on the size of the molecule. i.e. bigger the molecule --> more the number of bonds --> higher the energy require to break the bond for vaporization --> consequently, higher the boiling point. If u look at the periodic table, you will find Br in the row lower than Cl meaning Br atom is bigger than Cl ( note: the size of atom or atomic radius increases as you go down the periodic table). That's why HBr has greater boiling point than HCl.

You are welcome.

Can I ask you a question, what do you mean by dispersion forces?
I understood the concept By the way, thank you!

[Amelia]

oh, sorry. I thought you knew what it meant.

Definition of dispersion forces (also called London dispersion forces or Wander-wal's forces or induced dipole-induced dipole forces)
Dispersion is an intermolecular attraction force that exists between all molecules. These forces are the result of the movement of electrons which cause slight polar moments. Dispersion forces are generally very weak but as the molecular weight increases so does their strength.

The Dispersion force is due to the movement of electrons in a molecule or an atom, the electrons are in continuous motion. At any point of time at one part og hte molecule there will be one more electron than the other. This part of the molecule induces slightly negetice charge while the other part induces slightly positive charge. The attraction between non-polar molecules give rise to dispersion forces.

P.S- Hope it helped! Anytime.

[**RoRo**]

oh, sorry. I thought you knew what it meant.

Definition of dispersion forces (also called London dispersion forces or Wander-wal's forces or induced dipole-induced dipole forces)
Dispersion is an intermolecular attraction force that exists between all molecules. These forces are the result of the movement of electrons which cause slight polar moments. Dispersion forces are generally very weak but as the molecular weight increases so does their strength.

The Dispersion force is due to the movement of electrons in a molecule or an atom, the electrons are in continuous motion. At any point of time at one part og hte molecule there will be one more electron than the other. This part of the molecule induces slightly negetice charge while the other part induces slightly positive charge. The attraction between non-polar molecules give rise to dispersion forces.

P.S- Hope it helped! Anytime.

Yup, it did! Thank you!

Guess what? I knew all the other terms BUT dispersion forces! LOL

Thanks ALOT! 

[Amelia]

Yup, it did! Thank you!

Guess what? I knew all the other terms BUT dispersion forces! LOL

Thanks ALOT! 

Lol! I thought so.. but no matter.
 And its okay, if you thank just one time, you know.

[The Golden Girl =D]

D here are the ppm Questions I told you about .

1. a solution is prepared by dissloving 0.475g of (NH4)2SO4 (Mr =118)in enough of distilled water and the solution is made up to 2.0 dm3

Calculate the ppm of

a] NH4 +                b] SO4  2-

 BOLD is the charge

If possible, please check those answers with your teacher.

Answer from My Teacher :

A] n=M/Mr
      =0.475/118
      =0.00403

mass =n*Mr
  =0.00403*18*2
  =0.145g
  =1.45mg

conc=145mg/2L
    = 72.5 ppm

B] Mass=0.475 - 0.145
      =0.33g
      =33mg

conc = 33mg/2L
       =16.5ppm

=]

[elemis]

Your teacher is wrong, the Mr of Ammonium Sulphat is NOT 118. It is 132.

[The Golden Girl =D]

Your teacher is wrong, the Mr of Ammonium Sulphat is NOT 118. It is 132.

Ari , the Mr is Already written in the Question as 118 , Perhaps the Q is wrong

[The Golden Girl =D]

I have something to ask . My teacher said we have to know the Number of isomers of hydrocarbons from C1 to C6 just in case . So how many Isomers does a C1 to C6 each have ?

can someone tell me the numbers Please ?

Thanks In Advance

[tmisterr]

I have something to ask . My teacher said we have to know the Number of isomers of hydrocarbons from C1 to C6 just in case . So how many Isomers does a C1 to C6 each have ?

can someone tell me the numbers Please ?

Thanks In Advance

which class oh hydrocarbons?

[Deadly_king]

I have something to ask . My teacher said we have to know the Number of isomers of hydrocarbons from C1 to C6 just in case . So how many Isomers does a C1 to C6 each have ?

can someone tell me the numbers Please ?

Thanks In Advance

C1     -     CH₄     -    No other isomers

C2     -     C₂H₆   -    No other isomers

C3     -     C₃H₈   -    No other isomers

C4     -     C₄H₁₀  -   2 isomers in all

C5     -     C₅H₁₂  -   3 isomers in all

C6     -     C₆H₁₄  -   5 isomers in all

If you have time, do take a look at the attached powerpoint presentation. It describes all what you need to know in organic chemistry.