last assesment yay

steve_ell · 19 Jul 2004, 3:14 AM

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i have a prac test on tuesday... my last assesment and im having trouble with equilibrium and titration. i know the theory and what to do with titration... i was just wondering what sor of questions they ask........... ie the mole ones.

with equilibrium im realy having trouble with equasions and how to write them......... n e advice would be really appreciated.

thanx

~*HSC 4 life*~ · 20 Jul 2004, 1:35 AM

in titration they usually ask you to find the molarity of the analyte, using stoichiometry. Usually you are given the volume and concentration of the titrant, use the equation n= C x V to find the number of moles, use the mole ratio from the equation you the titration reaction to calculate no of moles of solution you wish to find molarity, then use C= N/V it's as simple as pie

In titration they may also describe the strength of the acids/bases they are using and ask you to choose a suitable indicator for the experiement

eg they might tell you that a strong base is beign titrated against a weak acid, so you might say phenolpthalein is a good choice as it can change colour between pH 8-10ish <-- remember a strong base and a weak acid will give a slightly basic solution

For equilibrium, you just have to write them as normal eq's with the double ended arrow...hmm id on't know if thats the help you needed...just make sure you practice a few in writing...in exams theyw ill usually get you to write the equil reactions you have seen before and should know eg carbon dioxide dissolving in water, auto dissociation of water, buffer systems such as hydrogen carbonate/hydrogen phosphate ions and the haber process (synthesis of ammonia)

More importantly, make sure you udnerstand equil reactions, exams tend to focus on how equil works rather than gettign you to write one down as they are usually given to you...know what happens to the position of equil when heat is increased, pressure increased, vol increased etc

Tommy_Lamp · 20 Jul 2004, 2:11 AM

pretty much comes down to...

C1V1 = C2V2

but they usually only ask for C since V is usually known

**CM_Tutor** · 22 Jul 2004, 3:12 PM

Please don't use the dilution formula C₁V₁ = C₂V₂ for titration calculations.

xiao1985 · 23 Jul 2004, 8:24 AM

Quote:

Originally Posted by CM_Tutor

Please don't use the dilution formula C₁V₁ = C₂V₂ for titration calculations.

lolz!!! couldn't agree more... try to use moles of reactants/products... tis more legit =)

kimmeh · 23 Jul 2004, 1:34 PM

i got told not to do that as well, incase they're in different ratios (corect me if i'm wrong)

**CM_Tutor** · 24 Jul 2004, 12:03 AM

Quote:

Originally Posted by xiao1985

lolz!!! couldn't agree more... try to use moles of reactants/products... tis more legit =)

We actually deduct marks from Uni students who use this approach, because it isn't really 'legit'.

19 Jul 2004, 3:14 AM	#1 (permalink)
steve_ell Assistant Member Join Date: Feb 2004 Posts: 57 Last Activity: 28 Oct 2004, 5:22 PM	last assesment yay You can hide this advertisement by registering. i have a prac test on tuesday... my last assesment and im having trouble with equilibrium and titration. i know the theory and what to do with titration... i was just wondering what sor of questions they ask........... ie the mole ones. with equilibrium im realy having trouble with equasions and how to write them......... n e advice would be really appreciated. thanx

20 Jul 2004, 2:11 AM	#3 (permalink)
Tommy_Lamp Coco HSC: 2004 Gender: Undisclosed Location: Northern Beaches Join Date: Jun 2004 Posts: 1,748 Last Activity: 1 Dec 2006, 11:48 AM	pretty much comes down to... C1V1 = C2V2 but they usually only ask for C since V is usually known __________________

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20 Jul 2004, 1:35 AM	#2 (permalink)
~HSC 4 life~ Ancient Orator HSC: N/A Gender: Undisclosed Join Date: Aug 2003 Posts: 2,762 Last Activity: 14 Jun 2009, 2:09 PM	in titration they usually ask you to find the molarity of the analyte, using stoichiometry. Usually you are given the volume and concentration of the titrant, use the equation n= C x V to find the number of moles, use the mole ratio from the equation you the titration reaction to calculate no of moles of solution you wish to find molarity, then use C= N/V it's as simple as pie In titration they may also describe the strength of the acids/bases they are using and ask you to choose a suitable indicator for the experiement eg they might tell you that a strong base is beign titrated against a weak acid, so you might say phenolpthalein is a good choice as it can change colour between pH 8-10ish <-- remember a strong base and a weak acid will give a slightly basic solution For equilibrium, you just have to write them as normal eq's with the double ended arrow...hmm id on't know if thats the help you needed...just make sure you practice a few in writing...in exams theyw ill usually get you to write the equil reactions you have seen before and should know eg carbon dioxide dissolving in water, auto dissociation of water, buffer systems such as hydrogen carbonate/hydrogen phosphate ions and the haber process (synthesis of ammonia) More importantly, make sure you udnerstand equil reactions, exams tend to focus on how equil works rather than gettign you to write one down as they are usually given to you...know what happens to the position of equil when heat is increased, pressure increased, vol increased etc

22 Jul 2004, 3:12 PM	#4 (permalink)
CM_Tutor Teacher Join Date: Mar 2004 Posts: 1,293 Last Activity: 22 Oct 2004, 12:23 AM	Please don't use the dilution formula C₁V₁ = C₂V₂ for titration calculations.

23 Jul 2004, 1:34 PM	#6 (permalink)
kimmeh Sleeping HSC: 2004 Gender: Female Location: Stables, Paddocks, Pens, Kennels, Cages Join Date: Jul 2003 Posts: 4,492 Last Activity: 25 Jul 2008, 1:34 PM	i got told not to do that as well, incase they're in different ratios (corect me if i'm wrong)