It's because calcium sulphate is a precipitate so it will coat the limestone and prevent it from reacting with the sulphuric acid. Therefore the reaction stops.
However calcium nitrate is an aqueous solution so the reaction continues at a steady rate.

Original post by THEMathlete

Different acids make different salts...
So
Calcium carbonate + Nitric Acid ---> calcium nitrate + water + carbon dioxide
So nitric acid reacts with it to make a nitrate salt.

Dunno why it's three marks though

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Reply 64

MissMedicine

1

What does everyone know about the Miller-Urey experiment? I don't understand it...

Reply 65

TherHig

7

Original post by randomer44

as in depth as the question asks (if its in the exam) could be 1 mark or 6 marks. atoms are the small individual parts in an element. elements consist of one type of atom only. ions are just atoms that are charged (i.e. positive or negative) this happens in ionic bonding when atoms give or take electrons to get a full outer shell (to be stable). a molecule is when 2 or more atoms join together (like oxygen), but im not sure about this one

so are hydrocarbons both molecules and compounds? :rolleyes:

also do we need to know any more of electrolysis other than that its the process of extracting metals using electricity?

A molecule is formed when two or more atoms join together chemically. A compound is a molecule that contains at least two different elements. All compounds are molecules but not all molecules are compounds

Reply 66

qudsia

Original post by AparnaX

You don't need to know about the electrolysis of aluminium for core. That was for additional.

For core the spec says

1.

Aluminium and titanium cannot be extracted fromtheir oxides by reduction with carbon. Details of the methods of extraction aren't required. Currentmethods of extraction are expensive because:

2.

there are many stages in the processes

3.

large amounts of energy are needed.

You just need to know that aluminium is more reactive than carbon, therefore it has to be extracted using electrolysis of molten compounds.

Electrolysis is basically using electricity to decompose (break down) a substance. I'll use the example of copper because this is the one we need to know.

As you can see the the copper has been dissolved to form a solution of copper sulphate. This means the ions can move. The positive copper ions are attracted to the negative electrode and the negative ions are attracted to the positive electrode.

Thanks alot!

Reply 67

getjob5

15

Original post by spike3601

Guys, do we need to know about isotopes for this C1 exam?

nope

Reply 68

getjob5

15

Original post by MissMedicine

What does everyone know about the Miller-Urey experiment? I don't understand it...

miller and urey setup an experiment with the basic components thought to have existed in primordial earth (water, ammonia, methane, hydrogen.) then they began introducing natural conditions such as heat (such as that from a volcano) and electricity (like a lightning bolt). after as little as a week of these conditions in a closed environment, they began to see simple organic molecules (e.g. amino acids,)

http://www.youtube.com/watch?v=CxA2IK9ppO4

Reply 69

briannax

Do you reckon Miller Urey will come up? It's been on a lot of the past papers. I think something about polymers will definately come up

Reply 70

nomorerevision

4

Original post by MissMedicine

What does everyone know about the Miller-Urey experiment? I don't understand it...

try this video :smile:

http://www.my-gcsescience.com/revision/core/the-miller-urey-experiment

Reply 71

unoriginalname1

I know its a big ask, but can anyone explain in detail alkenes, alkanes, polymers and monomers please? some reference to hydrocarbons and their structure e.g. double bonds, saturated etc.

Thanks in advance

Reply 72

THEMathlete

12

Original post by MissMedicine

It's because calcium sulphate is a precipitate so it will coat the limestone and prevent it from reacting with the sulphuric acid. Therefore the reaction stops.
However calcium nitrate is an aqueous solution so the reaction continues at a steady rate.

Yeah my answer was completely wrong :tongue:

woops

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Reply 73

MissMedicine

1

Thank you so much! :biggrin:

Original post by nomorerevision

try this video :smile:

http://www.my-gcsescience.com/revision/core/the-miller-urey-experiment

Reply 74

MissMedicine

1

Original post by Sophsha

miller and urey setup an experiment with the basic components thought to have existed in primordial earth (water, ammonia, methane, hydrogen.) then they began introducing natural conditions such as heat (such as that from a volcano) and electricity (like a lightning bolt). after as little as a week of these conditions in a closed environment, they began to see simple organic molecules (e.g. amino acids,)

http://www.youtube.com/watch?v=CxA2IK9ppO4

Thank you! :biggrin:

Reply 75

xxxKINGxxx

10

Original post by briannax

Do you reckon Miller Urey will come up? It's been on a lot of the past papers. I think something about polymers will definately come up

There was a 4 marker on structure of polymers in C2 in the exam I took in May. Dunno if they'll put a lot on it on C1 as well.

Reply 76

xxxKINGxxx

10

Original post by unoriginalname1

I know its a big ask, but can anyone explain in detail alkenes, alkanes, polymers and monomers please? some reference to hydrocarbons and their structure e.g. double bonds, saturated etc.

Thanks in advance

Crude oil seperated by fractional distillation - seperating molecules from a mixture. By evaporating basically everything, then having seperate fractions where the parts are separated as they condense at different temperatures.

Hydrocarbons = Molecules with only hydrogen/carbon.
Alkanes only have single bonds, so their chemical stick diagram would kinda look like c-c-c with 2 hydrogen atoms attached on each carbon atom, but the carbon atoms are the end have 3 hydrogen atoms attached giving it a general formula of Cn H2n+2.

EXAMPLE: Propane http://upload.wikimedia.org/wikipedia/commons/a/a2/Propane-2D-flat.png

Alkenes have a double bond. All the alkenes we need to know only have one double bond.
EXAMPLE: Propene http://www.gcsescience.com/Propene.gif (You don't need to know how to draw alkenes i think.
They have a general formula of Cn H2n

Cracking = Splitting an Alkane into a smaller Alkane and a Alkene (Which is mainly to make plastics) This is done by heating the alkane with a catalyst.

Alkanes are saturated - I.E they have the hydrogen atoms at the end, so they can't expand.
Alkenes are unsaturated - They don't have the hydrogen atoms at the end.

Test for alkenes is bromine water. Bromine turns colourless when reacted with an unsaturated hydrocarbon.

Polymers are made by combining monomers. That is done by breaking the double bond, so the monomers start to form chains. The longer the chain in hydrocarbons, the higher the evaporation point, the higher the viscosity (Viscosity = The rate it flows at e.g Honey High Viscosity, Water low)

This is what should be drawn when asked to show formation of polymers.
http://www.bbc.co.uk/schools/gcsebitesize/science/images/gcsechem_29.gif

For food, animal fats = Saturated. Plant fats (Oil) = Unsaturated.
To make oil solid, you go through hydrogenation. This is done by reacting the oil with hydrogen at 60 degrees with a nickel catalyst. You want to do this so you have your spreadable butter, not crappy olive oil to put on your toast.

Thats basically it, in addition to environmental and health effects but thats really just common sense