Covalent Compounds And Seperation Techniques

Question 1

What’s is covalent bonding

Answer 1

A shared pair of electrons between two atoms
Each atom involved must have enough covalent binds to fill its outer shell
Between two non metals
Forms a molecule

Question 2

What happens in the covalent bond of hydrogen

Answer 2

Hydrogen atoms just need one more electron to fill their outer shell so they form a covalent bond with one other hydrogen atom to make h2

Question 3

What happens in the covalent bond of hydrogen chloride

Answer 3

Both atoms only need one more electron to fill their outer shell so only need one covalent bond and form HCL

Question 4

What happens in the covalent bond of methane

Answer 4

Carbon has four outer electrons so it needs four hydrogen atoms to form covalent bonds with to get a full outer shell and form CH4

Question 5

What happens in the covalent bonding of oxygen

Answer 5

Oxygen atoms have six outer electrons so they must share two electrons to get eight electrons at the end and form O2

Question 6

What happens in the covalent bond of water

Answer 6

The oxygen needs two more outer electrons so it shares one electron with two hydrogen atoms to form H2O

Question 7

What happens in the covalent bond of carbon dioxide

Answer 7

Two oxygen atoms share electrons with a carbon atom to create CO2

Question 8

What are the properties of simple molecular covalent substances

Answer 8

The bonds are strong but the forces of attraction are weak
The melting and boiling points are very low because of this and most substances are liquid or gas at room temperature
There are no ions so they can’t conduct electricity

Question 9

What are the properties of giant molecular covalent substances

Answer 9

They are like ionic lattices but there are no charged ions
All atoms are bonded by strong covalent bonds
They have very high melting and boiling points
They’re insoluble in water
They can’t conduct electricity except from graphite

Question 10

What are the properties of diamond

Answer 10

Made of carbon only
Each carbon atom has covalent bonds to 4 other carbon atoms
It’s really hard and can be good for cutting tools
There are no free electrons so it won’t conduct electricity p

Question 11

What are the properties of graphite

Answer 11

Each carbon atom forms three covalent bonds to other carbon atoms this creates sheets of carbon atoms that can easily slide over each other so it’s a good lubricant
The layers can slide off like in a pencil they slide off onto the paper
There’s lots of delocalised electrons so it can conduct electricity so can be used for electrodes

Question 12

What does miscible mean

Answer 12

When two liquids are put together and they mix with each other

Question 13

What is an immiscible liquid

Answer 13

When two liquids are put together and they don’t mix they create layers that sit on top of each other

Question 14

How are immiscible liquids seperatedn

Answer 14

Using a separating funnel
When left to stand the denser liquid sinks to the bottom and the lighter on floats on top of it
The tap is opened to drain off the denser liquid then closed to stop the lighter one from coming trough

Question 15

How are miscible liquids separated

Answer 15

By fractional distillation
They must have different boiling points so when the mixture is heated they will condense at different temperatures and can be collected separately

Question 16

How is air fractionally distilled

Answer 16

It is filtered to remove dust
Cooled to around -200c and becomes a miscible liquid
In the cooling water vapour condenses and can be removed
The liquified air enters the column and is heated slowly
Oxygen and argon come out of the bottom and another column is used to separate them and nitrogen gas comes out of the top

Question 17

What is chromatography

Answer 17

It is used to identify substances in a mixture because substances travel through paper at different speeds

Question 18

How do you do chromatography

Answer 18

Put spots of each mixture being tested on as pencil baseline of the paper
Roll up the paper and put it in a beaker containing a solvent keeping the baseline above the level of water
The solvent moves up the paper taking the samples with it
Different chemicals in the samples form different spots on the paper

Question 19

What is the r value of a chromatogram

Answer 19

The ratio between the distance travelled by the dissolved substance and the distance travelled by the solvent
Each substance will have s different r value

R = distance travelled by substance/ distance travelled by substance