HELP HELP!

[Lost_Life]

Can someone explain percentage error calculation? :/

its the mass thats given over the mass you had at the beginning... i need an example to explain it better..

 

[Lost_Life]

 

[Mewan95]

its the mass thats given over the mass you had at the beginning... i need an example to explain it better..

Thats the percentage yield. Im talkin about the percentage error or percentage uncertainty...

 

[aniekan]

Can someone explain percentage error calculation? :/

= Error/actual measurement * 100

Example .

56cm3 of Hydrogen was given off in a reaction between Mg and HCl . Assuming reading accuracy of the measuring cylinder is + or - 3 . Find the percentage error.

3/56 * 100 = + or - 5.4%

Or :

The actual mass of a compound is 46.86g and the measured mass is 49.86g find the percentage error .

Wrong measurement - actual measurement / actual measurement * 1oo

49.86 - 46.86/ 46.86 * 100 = 6.4 %

 

[aniekan]

View attachment 20111

that's a nice and easy trick I mole of a substance will contain exactly the same number of atoms as they are in 12g of carbon 12 therefore there is no difference. Both contain same number of atoms

 

[Mewan95]

= Error/actual measurement * 100

Yeah i know that. But sometimes they multiply the error by another number. How do u find that number?

 

[Lost_Life]

Thats the percentage yield. Im talkin about the percentage error or percentage uncertainty...

Generally asked for apparatuses like cylinders or temperature of +-0.05?

 

[Mewan95]

Generally asked for apparatuses like cylinders or temperature of +-0.05?

Yeah. Thats correct.

 

[tom850]

ah..the mark scheme.. i checked it out too. but i didn't know how..??

Im going through it now .. It is an endothermic reaction.
Youh got it eh I didn but..

 

[Lost_Life]

Yeah. Thats correct.

yeh so basically its the error/the actual thing *100... smetimes for the mass you need to check the equation and check the mole ratio.. for ex:.mass used for KHCO3= 2.00g and in the equation its 2KHCO3 error of mass =+-0.01g... therefore 2*0.01/2.00 *100

 

[Lost_Life]

Im going through it now .. It is an endothermic reaction.
Youh got it eh I didn but..

you're dehydrating the crystals..

 

[Mewan95]

yeh so basically its the error/the actual thing *100... smetimes for the mass you need to check the equation and check the mole ratio.. for ex:.mass used for KHCO3= 2.00g and in the equation its 2KHCO3 error of mass =+-0.01g... therefore 2*0.01/2.00 *100

Thanks alot!

 

[Lost_Life]

Thanks alot!

no problem. Glad i helped

 

[Mewan95]

Can someone help me with the Iodine-thiosulfate titrations? like explain it to me. The calculations and steps.

 

[aniekan]

Can someone help me with the Iodine-thiosulfate titrations? like explain it to me. The calculations and steps.

where did you find that?

 

[Mewan95]

where did you find that?

Its there on the June 2010 Unit 3 paper. Question 3. Its about that titration. In my text book they have that topic but i don't completely understand the calculations. That is why i would like someone to explain it to me.

 

[aniekan]

Its there on the June 2010 Unit 3 paper. Question 3. Its about that titration. In my text book they have that topic but i don't completely understand the calculations. That is why i would like someone to explain it to me.

I have Unit 3 in June so I can't help sorry

 

[Mewan95]

Anyone who can help me asap? My Unit 3 paper is tmrw.

 

[shoaeb]

im giving unit 3b chemistry tommorrow..edexcel
if any one has some questions related to that let me know..i would love to discuss them over here.

 

[tom850]

you're dehydrating the crystals..

;D.. Juz Came Bak Aftr Exam Chem 3b:/ Have You Done Well ^.^
Im Bit Nervous Cuz I Did Mistakes