mean titre?

ive been looking at some pract papers for my exam tomz, and going through things i havent learnt in class, and just wanna double check im right.

i the mean titre, like the mean of all titration results. and it is add all of them divided by how many titrations were done, right?

Reply 1

medicinemad

yep yep that's right.calculate your titres to 2.d.p :biggrin:

Reply 2

jones001

OP

thanks =] oh and ive always had trouble with ionic equations, i always seem to mess it up, cos i dont know wat im meant to be doing, can someone briefly show me how to do one step by step??? it would be helpful, oh and something is an oxidising agent, only if it loses electrons???

Reply 3

Excalibur

15

For the titration question, make sure not to use the first one if it's not concordant (within ±0.2cm3) with the others because the first one is a rough titration.

---

Oxidising agent = oxidises something else = removes electrons from something = itself gets reduced = so itself gains electrons.

Reducing agent = reduces something else = donates electrons to something = itself gets oxidised = so itself loses electrons.

The steps to writing an ionic equation from a full equation is:
1) Write out the full equation.
2) Write all the soluble ionic compounds with their ions separated.
3) Write all insoluble ionic compounds, covalent compounds and everything else normally.
4) Cross out ions which appear on both sides - these are the spectator ions.

So for example:

NaCl (aq) + AgNO3 (aq) --> NaNO3 (aq) + AgCl (s)

Separating ions give:

Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) --> Na+(aq) + NO3-(aq) + AgCl(s)

Deleting the spectator ions that appear on both sides, namely Na+ and NO3-, you get:

Ag+(aq) + Cl-(aq) --> AgCl (s)

Ionic half equations in redox reactions are a bit different too.

Reply 4

Stranded

11

medicinemad

yep yep that's right.calculate your titres to 2.d.p :biggrin:

You mean the mean titre should be stated to 2 decimal places?

Reply 5

Stranded

11

Excalibur

For the titration question, make sure not to use the first one if it's not concordant (within ±0.2cm3) with the others because the first one is a rough titration.

---

Oxidising agent = oxidises something else = removes electrons from something = itself gets reduced = so itself gains electrons.

Reducing agent = reduces something else = donates electrons to something = itself gets oxidised = so itself loses electrons.

The steps to writing an ionic equation from a full equation is:
1) Write out the full equation.
2) Write all the soluble ionic compounds with their ions separated.
3) Write all insoluble ionic compounds, covalent compounds and everything else normally.
4) Cross out ions which appear on both sides - these are the spectator ions.

So for example:

NaCl (aq) + AgNO3 (aq) --> NaNO3 (aq) + AgCl (s)

Separating ions give:

Na+(aq) + Cl-(aq) + Ag+(aq) + NO3-(aq) --> Na+(aq) + NO3-(aq) + AgCl(s)

Deleting the spectator ions that appear on both sides, namely Na+ and NO3-, you get:

Ag+(aq) + Cl-(aq) --> AgCl (s)

Ionic half equations in redox reactions are a bit different too.