Qualification > Sciences
CHEM AND BIO HELP AND TIPS HERE
Helium:
--- Quote from: Ivo on June 06, 2010, 12:10:20 pm ---Yes.
--- End quote ---
Ok got it Thanks,,
In calculations of moles is there a fixed rounding point,
like 2 d.p ,
Ivo:
--- Quote from: Helium on June 06, 2010, 12:16:47 pm ---Ok got it Thanks,,
In calculations of moles is there a fixed rounding point,
like 2 d.p ,
--- End quote ---
Doesn't really matter as long as you keep it constant. So use 2dp throughout or 3sf, you choose! ;)
MasterMath:
--- Quote from: bored2death on June 06, 2010, 12:11:34 pm ---aqueous refers to dilute ... as in it contains a high concentration of water molecules.
--- End quote ---
Not exactly .. Aq. means that the solvent is water ( i.e its disolved in water) it can STILL be CONCETRATED.
bored2death:
--- Quote from: CatAly$t on June 06, 2010, 11:53:03 am ---how do we know which reagent is in excess??
and how do u solve the fourth question??
--- End quote ---
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:
--- Quote from: MasterMath on June 06, 2010, 12:19:50 pm ---Not exactly .. Aq. means that the solvent is water ( i.e its disolved in water) it can STILL be CONCETRATED.
--- End quote ---
Yeah I can see what you're saying.. but you can relate (in a weird way :P) 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)
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