GRAVIMETRIC ANALYSIS ERRORS UNDERSTANDING HELP!!

[aronno]

 

CAN ANYBODY MAKE A SUMMARY FOR THE ERRORS THAT CAUSE NO EFFECT ON THE RESULTS AND THE ONES THAT OVERESTIMATE AND UNDERESTIMATE THE RESUTS.

INCLUDE DIAGRAMS IF U CAN.... (pleeeeeeeeeeeeeeeeeaaaaaaaaaseeeeeee!)

IT IS DEAD URGENT!!!    :buck2:

THANKS AHEAD

[hard]

what the hell?

[bucket]

in other words, do your homework? lol
nah mate.

[Edmund]

I think I get what you are trying to ask. It would help if you could put a question here...

Its something like this:

Error: Pipette used to draw acid into beaker is wet. This results in a weaker acid.

When titration is carried out, less base is needed to neutralise this acid.

Less base required > lower titre

Then you should be able to deduce how the other calculations can be affected because of the lower titre.

Work backwards.

[bucket]

I think I get what you are trying to ask. It would help if you could put a question here...

Its something like this:

Error: Pipette used to draw acid into beaker is wet. This results in a weaker acid.

When titration is carried out, less base is needed to neutralise this acid.

Less base required > lower titre

Then you should be able to deduce how the other calculations can be affected because of the lower titre.

Work backwards.

The title clearly said GRAVIMETRIC not VOLUMETRIC.
ie. Precipitate not completely dry = added weight = more substance being used in calculations than what is actually there = over estimation.

[Edmund]

Whoops sorry...

Exactly one year since Ive done it...

[aronno]

IN simpler terms can some ]one list the possible errors that can occur the experiement!!!!

that can give u a higher than normal result, lower than normal result and errors that dont effect the outcome.

thanks peeps

 

[Edmund]

As stated by bucket:

ie. Precipitate not completely dry = added weight = more substance being used in calculations than what is actually there = over estimation.

Insoluble substances in precipitate = over estimation

Reaction during the formation of precipitate causing other substances to form = greater mass = over estimation

and

Lost precipitate = less mass = less substance in calculations = under estimation

[bucket]

and not all of the substance being mesaured precipitating = less mass used in calculations than what was in the original sample = under estimation.
I can't think of any more.

[Mao]

the most commonly overlooked one: more than one source of ion in the original sample, overestimation

This is especially the case with the common gravimetric analysis for salt content, which assumes the chloride ion is only present as NaCl.

[aronno]

thanks guys!!!

[/0]

When rinsing the precipitate you could use too much water and dissolve some of the sample (if the sample is only partially insoluble) => lower percentage recorded
Not fully precipitating the salt => lower percentage recorded
Excess de-ionised water in conical flask => no effect, moles of salt stays the same
Excess de-ionised water in pipette => less moles of salt => lower percentage recorded

[d0minicz]

-When drying the precipitate in the oven, some can decompose at high temperatures.

-Weighing errors (eg: digital vs analog)

-Some solids may be lost during filtration

[Mao]

Excess de-ionised water in pipette => less moles of salt => lower percentage recorded

pipettes are used in gravimetric analysis?

-When drying the precipitate in the oven, some can decompose at high temperatures.

so long as they don't decompose and become airborne, you should have little concern because of the conservation of mass.

[/0]

Excess de-ionised water in pipette => less moles of salt => lower percentage recorded

pipettes are used in gravimetric analysis?

-When drying the precipitate in the oven, some can decompose at high temperatures.

so long as they don't decompose and become airborne, you should have little concern because of the conservation of mass.

It could be used like:
- dilute sample to 250mL
- precipitate
- pipette 20mL into conical flask
- dry sample

I guess it isn't necessary but whatever