Edexcel CHEMISTRY DOUBTS!!!!

[guMnam]

I'm sorry for taking too long , I had to call my friend for this.

Hmm it's an follows as Nobody said ;

Look, initially, you've got H2SO4(aq) giving 3 ions
now, when you add barium hydroxide, it will form a precipitate and take out all the sulphate ions in the form of BaSO4(s) and further neutralise the hydrogen ions which fill form 2H2O(l).
oaky? so, at that time, the conductivity decreases.

Now, when all the sulfuric acid is neutralized... barium ions and hydroxide ions will be generated when Ba(OH)2(aq) reacts.
which will lead to an increase in the conductivity.



My friend's/teacher's explanation ;

as bRIUM HYDROXIDE IS added it's ions eat up the acid ions. hence no ions , cuz all ions cancel each other , electrical conductivity falls  to 0 ..On more addition of bariium hydroxide , OH- increases , i.e.e the -ve charge increases , hence electrical conductivity increases .

GG

Thanks i had the same doubt .. but i got the corerect ans AND A rong explanation

[The Golden Girl =D]

LOL xD

[**RoRo**]

Question, do we need to study Unit 1 for Unit 2 as well, especially energetics and organic chemistry [the whole thing]?

[The Golden Girl =D]

Only the Organic chapter and  have a general Idea of the graphs for the exo and endo rxns.

Good Luck

[**RoRo**]

Only the Organic chapter and  have a general Idea of the graphs for the exo and endo rxns.

Good Luck

Expected so [organic]!
Thank you & good luck to you too!

[The Golden Girl =D]

Welcome

[Blizz_rb93]

Give 2 reasons why chlorinated hydrocarbons are not used today in fire extinguishers?

and

Suggest why chlorine-based insecticides last a long time in the soil?

if anyone knows where i can get the teachers book for the edexcel AS chemistry, that would be very helpful

Thank you

[Master_Key]

Give 2 reasons why chlorinated hydrocarbons are not used today in fire extinguishers?

and

Suggest why chlorine-based insecticides last a long time in the soil?

if anyone knows where i can get the teachers book for the edexcel AS chemistry, that would be very helpful

Thank you

Chlorinated HC cause damage to ozone layer. They are stable so reach ozone layer quickly.
Chlorine radical are formed in fire.

[NidZ- Hero]

Whats the difference between Nuclear charge and effective nuclear charge?

[EMO123]

Whats the difference between Nuclear charge and effective nuclear charge?

http://answers.yahoo.com/question/index?qid=20101004142249AAzpUkI
hope it helped

[NidZ- Hero]

http://answers.yahoo.com/question/index?qid=20101004142249AAzpUkI
hope it helped

I read this before... but know i understood
well its lke this
 a fluorine atom has an electronic structure of 1s2 2s2 2px2 2py2 2pz1. It has 9 protons in the nucleus.

The incoming electron enters the 2-level, and is screened from the nucleus by the two 1s2 electrons. It therefore feels a net attraction from the nucleus of 7+ (9 protons less the 2 screening electrons).

By contrast, chlorine has the electronic structure 1s2 2s2 2p6 3s2 3px2 3py2 3pz1. It has 17 protons in the nucleus.

But again the incoming electron feels a net attraction from the nucleus of 7+ (17 protons less the 10 screening electrons in the first and second levels).


Nucleur charge = proton number
Effective nuclear charge = Nucleur charge- no.of screening electrons

is that rght ?

[EMO123]

I read this before... but know i understood
well its lke this
 a fluorine atom has an electronic structure of 1s2 2s2 2px2 2py2 2pz1. It has 9 protons in the nucleus.

The incoming electron enters the 2-level, and is screened from the nucleus by the two 1s2 electrons. It therefore feels a net attraction from the nucleus of 7+ (9 protons less the 2 screening electrons).

By contrast, chlorine has the electronic structure 1s2 2s2 2p6 3s2 3px2 3py2 3pz1. It has 17 protons in the nucleus.

But again the incoming electron feels a net attraction from the nucleus of 7+ (17 protons less the 10 screening electrons in the first and second levels).


Nucleur charge = proton number
Effective nuclear charge = Nucleur charge- no.of screening electrons

is that rght ?

ya it is right

[Master_Key]

I read this before... but know i understood
well its lke this
 a fluorine atom has an electronic structure of 1s2 2s2 2px2 2py2 2pz1. It has 9 protons in the nucleus.

The incoming electron enters the 2-level, and is screened from the nucleus by the two 1s2 electrons. It therefore feels a net attraction from the nucleus of 7+ (9 protons less the 2 screening electrons).

By contrast, chlorine has the electronic structure 1s2 2s2 2p6 3s2 3px2 3py2 3pz1. It has 17 protons in the nucleus.

But again the incoming electron feels a net attraction from the nucleus of 7+ (17 protons less the 10 screening electrons in the first and second levels).


Nucleur charge = proton number
Effective nuclear charge = Nucleur charge- no.of screening electrons

is that rght ?

Its shielding electrons.

Chlorine has same E.N.C. The electrons are held far and thus the ionisation energies and properties like that are less when compared to Fluorine. For attraction you need to consider both.
Effective nuclear charge and distance from nucleus.

[**RoRo**]

Question, are we supposed to know the ionic equations for the common oxidizing/reducing agents like Manganate (VII), Dichromate (VI), Hydrogen peroxide, concentrated sulphuric acid, potassium iodide, etc?

& when the branching in alkanes increases, the melting point increases or decreases and why?

Thank you

[Malak]

Question, are we supposed to know the ionic equations for the common oxidizing/reducing agents like Manganate (VII), Dichromate (VI), Hydrogen peroxide, concentrated sulphuric acid, potassium iodide, etc?

& when the branching in alkanes increases, the melting point increases or decreases and why?

Thank you

I dont think u need to memories those equations, but then u should know how to write ionic equations generally in case it comes up.

When branching increases the melting point decreases because the atoms are less packed together and therefore the intermolecular forces are weaker