chemistry practical doubt-smallest division and estimated error

[princess787]

hey guys.. in chem practicals there is often a question regarding the estimated error, and something about smallest division.. can u please help me in understanding it? i heard from one of my classmates that the estimated error is half of the smallest division.. and then while calculating the percentage error in a reading.. then we divide the estimated error by then reading or the smallest division! please help! got my exams tomo!

 

[PrincessLuna]

Its

hey guys.. in chem practicals there is often a question regarding the estimated error, and something about smallest division.. can u please help me in understanding it? i heard from one of my classmates that the estimated error is half of the smallest division.. and then while calculating the percentage error in a reading.. then we divide the estimated error by then reading or the smallest division! please help! got my exams tomo!

Half smallest division in instrument divided by 2.

If asked for % error, take error instrument (half division), divided by a measurement you took then times 100.


Note when 2 measurements are taken like in a burette one initial, one final then titral value's uncertainity is sum of uncertainty of initial and final. (but even if you don't sum cie gives you marks)

 

[PrincessLuna]

hey guys.. in chem practicals there is often a question regarding the estimated error, and something about smallest division.. can u please help me in understanding it? i heard from one of my classmates that the estimated error is half of the smallest division.. and then while calculating the percentage error in a reading.. then we divide the estimated error by then reading or the smallest division! please help! got my exams tomo!

E.g for burette

Uncertainty in instrument 1cm3 / 2 = plus or minus 0.5cm3

Percentage uncertainty in calculated value, say you took initial reading 23cm3, 0.5/23 X 100= plus or minus 2.2%

 

[princess787]

oh thanks! and does the rough titration have decimal like 24.0 cm cube or just 24 cm cube

 

[PrincessLuna]

oh thanks! and does the rough titration have decimal like 24.0 cm cube or just 24 cm cube

Needs decimals, I'd advice putting it to 2dp for all sets of values and make sure you use same amount of dp for all values else you will lose marks.

If there is anything with temperature such as titrating with a thermometer (see J13 p31), you must take thermometer readings to 1dp even if the instrument does not have .5 scale and at least one of your readings must have .0 and .5 in them.

 

[princess787]

oh thanks really really a lot!

 

[PrincessLuna]

oh thanks really really a lot!

You're really really welcome.