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Ocr f321 23 may 2013~official discussion thread watch

1. (Original post by imgonnafail)
When rearranging the n=(cv)/1000 equation to work out concentration, what is the equation??? Is it c=(n)x1000/vol?
Absolutely Correct!

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2. (Original post by Ché.)
You're so very welcome!
Was it clear enough!?

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Very

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3. (Original post by Ché.)
Do you want to go through anything quickly now?
A little revision session!

You'll be fine...
I am not s******g myself as such, and I have a two-hour AS Listening, Reading and Writing Spanish Examination FIRST!
You'll be fine!

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test me. i get everything except from that (V) in naames..
i forgot how to do them
4. He is gone> anyone else/ Wanna test each other??

How are Van Der Waals formed?
5. (Original post by Freddy-Francis)
He is gone> anyone else/ Wanna test each other??

How are Van Der Waals formed?
I am here!
Sorry!

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6. (Original post by Freddy-Francis)
He is gone> anyone else/ Wanna test each other??

How are Van Der Waals formed?
Right...
- Oscillations form within the orbital regions of the atoms.
- This creates a distribution of charge - one side becoming slight positive and slight negative.
- This provokes instantaneous dipoles with neighbouring molecules forming intermolecular forces we know as VDW!

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7. (Original post by Freddy-Francis)
test me. i get everything except from that (V) in naames..
i forgot how to do them
Right...
"Explain the difference in boiling points between Chlorine, Bromine and Iodine."

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8. Permanent dipoles?
9. (Original post by Ché.)
Right...
"Explain the difference in boiling points between Chlorine, Bromine and Iodine."

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The boiling points increase down group 7. This is because the number of electrons increase and thus do the strength of van der waals. Iodine has the biggest boiling point while Chlorine has the lowest.

More shells down the group. The larger number of shells, then the greater the shielding effect and the smaller the nuclear attracting experienced by the outer electrons
10. OK. Anomalous properties of water?
11. (Original post by Freddy-Francis)
The boiling points increase down group 7. This is because the number of electrons increase and thus do the strength of van der waals. Iodine has the biggest boiling point while Chlorine has the lowest.

More shells down the group. The larger number of shells, then the greater the shielding effect and the smaller the nuclear attracting experienced by the outer electrons
Correct!
You got this, you got this!

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12. I get messed up on the basic ones like that (V) sytamatic name.. Please explain /
13. Right, here it goes...

ANOMALOUS PROPERTIES:
- High melting and boiling points explained with possible reference to the consequence of higher densities.
- High surface tension and viscosity - that is why insects can walk on water!
- Ice Vs. Water - Ice is less dense that in liquid form as it consists of an open lattice having low densities than liquid.
- Solubility of water = High freezing points!
- explanation further that hydrogen bonding is the strongest of the intermolecular bonding and requires higher amounts of energy to break the molecules apart.

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14. Trends in Ionisation energy?
And why does Oxygen have a lower ionisation energy to Nitrogen?
15. (Original post by Freddy-Francis)
I get messed up on the basic ones like that (V) sytamatic name.. Please explain /
Sure!
You have to with the logic... It sometimes bewilders me.
Ignore the atom you're obviously trying to find the oxidation number of with a oxyanion normally!
Let's say we have oxygen atoms within the compound, work out their accumulative charges and they you want to find the charge need to equalise the charges to 0.

So...
For example,
NO3 - it obtains a overall -1 charge; the oxygen atoms give you -6 so you will need 5 (V) charge on the nitrogen to give the appropriate charge!

Clear?.
I hope so!
It is so fussing for 1/2 marks!

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16. (Original post by PreppyNinja)
Trends in Ionisation energy?
And why does Oxygen have a lower ionisation energy to Nitrogen?
I thought ionisation energy increased across periods and decreased down the groups :O

THen how come oxygen have lower IE
17. (Original post by Ché.)
Sure!
You have to with the logic... It sometimes bewilders me.
Ignore the atom you're obviously trying to find the oxidation number of with a oxyanion normally!
Let's say we have oxygen atoms within the compound, work out their accumulative charges and they you want to find the charge need to equalise the charges to 0.

So...
For example,
NO3 - it obtains a overall -1 charge; the oxygen atoms give you -6 so you will need 5 (V) charge on the nitrogen to give the appropriate charge!

Clear?.
I hope so!
It is so fussing for 1/2 marks!

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oh ok..
18. Could someone quickly bullet point everything about permanent dipole-dipole forces? 😣

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19. (Original post by yasmin.mahfouz)
Could someone quickly bullet point everything about permanent dipole-dipole forces? 😣

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They are weak attractive forces between permanent dipoles in neighbouring polar molecules.
20. (Original post by PreppyNinja)
Trends in Ionisation energy?
And why does Oxygen have a lower ionisation energy to Nitrogen?
Oxygen would obtain a lower ionisation energy as:
- It has a same identical atomic radius.
- The amount of electrons differ by one meaning that Oxygen will be able to remove that one easier!
- this complies with a reduction in nuclear attraction.
- Electron shielding wouldn't affect their energies in this context due them being in the same period!

ACROSS A PERIOD:
Ionisation would decrease - from left to right that is (with reasons above)

DOWN GROUPS:
Ionisation would decrease also because:
- The atomic radius increases down a group, increase susceptibility of electron removal.
- Electron shielding is increases meaning the attraction would decrease as the outermost electrons are further away from the nucleus.

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