CHEM AND BIO HELP AND TIPS HERE

[Lariemeeva]

https://studentforums.biz/index.php/topic,54.msg253414.html#msg253414
Here's the link posted by VIN. Sorry my net is really slow right now, I can hardly upload anything.

Here's my question.
Anyone can help me with Chemistry Oct/Nov 2009 P3, Q 5b, c (i) and (ii).
I'm really getting confused, and I'd appreciate an explanation on the whole hydride thing.

I still don't get it. Anyone can help?

[Ivo]

I still don't get it. Anyone can help?

You don't need to know about hydrides.  They tell you in the question: they are comparable to alkanes.

So, you just draw the structual formula of Ge4H10 (alkane would be C4H10).

We know products of combustion of alkanes are carbon dioxide and water, so simply for these hydrides it's germanium (IV) oxide and water.

[Helium]

how do we know which reagent is in excess??

and how do u solve the fourth question??

? Because they say grams we have to assume the Cl2 and S02 are solids not gases

right?

[Ivo]

? Because they say grams we have to assume the Cl2 and S02 are solids not gases

right?

Yes.

[bored2death]

aqueous refers to dilute ... as in it contains a high concentration of water molecules.

[Helium]

Yes.

Ok got it Thanks,,

In calculations of moles is there a fixed rounding point,

like 2 d.p ,

[Ivo]

Ok got it Thanks,,

In calculations of moles is there a fixed rounding point,

like 2 d.p ,

Doesn't really matter as long as you keep it constant.  So use 2dp throughout or 3sf, you choose! 

[MasterMath]

aqueous refers to dilute ... as in it contains a high concentration of water molecules.

Not exactly .. Aq. means that the solvent is water ( i.e its disolved in water) it can STILL be CONCETRATED.

[bored2death]

how do we know which reagent is in excess??

and how do u solve the fourth question??

firstly you have to calculate the number of moles and which ever has the most moles is the one in excess for example in the may june 2oo4 exam its between magnesium and ethanoic acid... u calculate the original number of moles ... n(Mg)= 3/24 = 0.125  AND of ethanoic acid = 0.2 mole ... this is considered the orginial the amount of moles u placed in the solution or reaction.. then u will say Mg is in excess because Mg can  only react with 2*0.125 moles of ethanoic acid which is 0.25 hence Mg is in excess get it?

[bored2death]

Not exactly .. Aq. means that the solvent is water ( i.e its disolved in water) it can STILL be CONCETRATED.

Yeah I can see what you're saying.. but you can relate (in a weird way ) to urine when its dilute  and when its concentrated u become constipated because there isnt enough water in ur system and fibre but thats not the point... In the chemistry study guide, most of the aqueous solutions have the same products or perhaps better to say ions H+ and OH- as dilute solutions ( unless they are transition elements or something like that)

[Helium]

So can anyone draw or find???

[Vin]

So can anyone draw or find???

Draw/Find what?

[Helium]

Draw/Find what?

By short,
Silicon carbide
Dimethyl sulphide, Germanium (IV) oxide,

Anyone Drew this??

can't get the first, want to make sure of the second

and

1 more Plzz, Whats with 09 and drawing
[/quote

PLZ

[soulreapr_ninja]

Fractional distillation of liquid air - HELP PLEASE!

Can someone post a link about it or so?

Fractional distillation of liquid air is a process used to separate liquids with different boiling points
this process is carried out in a fractioning column
Fractional Distillation of petrolleum:-

Natural Gas- for cooking
Gasoline-car fuel
Naphtha-for chemical industries
Kerosene-fuel in jet engines
Diesel Oil-fuel in diesel engines
Fuel Oil-fuel in ships
Lubricating oil-used in waxing and lubricating
Bitumen-for paving roads and isolation

As we go down the fractioning column frm natural gas to bitumen, the boiling point increases gradually.
Hope tht helped  

[Vin]

By short,
Silicon carbide
Dimethyl sulphide, Germanium (IV) oxide,


and

1 more Plzz, Whats with 09 and drawing
[/quote

PLZ

Rest coming up.. (hope its not too compli.)