Question

We were suppose to calculate the molar mass and then average that. After, calculate the standard deviation in molar mass and determine the unknown acid and it’s percent error. We did three runs and the numbers recorded are the mass of the unknown acid, initial and final burst readings, and the volume of NaOH solution. How do I do this?

Dete talieckar iobh t peed Wso hre n the wo mev

Answer 1

You are missing molarity of NaOH from above.

Once you have that, the procedure should be like this,

Say for run 1,

moles NaOH = molarity NaOH x volume NaOH added

moles acid = moles NaOH

molar mass acid = grams of acid taken/moles acid

So from the three runs,

calculate average molar mass = [molar mass run1 + molar mass run2 + molar mass run3]/3

This is mean molar mass

Identify the acid from lierature known molar masses of acids

Percent error in molar mass = [(literature molar mass - mean molar mass)(literature molar mass)] x 100

Ignore the signs here. Percent error is always +ve value.

Standard deviation

variance = [mean(inidivudal run molar mass - mean)^2/3]

standard deviation = sq.rt.(variance)