After you have weighed out the sample to improve precision as shown in the quest
ID: 875329 • Letter: A
Question
After you have weighed out the sample to improve precision as shown in the question above you can now speed up the titration by predicting how much titrant will be used for that sample size. This volume can be added to the initial buret reading to predict the final buret reading for a trial. You can then rapidly add titrant to within a mL of the predicted final volume and then carefully add the titrant to the end point.
Estimating amount of NaOH needed to approach 1 mL of the end point
If 6.45 mL NaOH was used in the titration of a 0.584 g sample of unknown, use ratios to determine the volume of NaOH needed in the next trial to titrate a sample mass of 0.934 g of your sample containing KHC8H4O4.
What will the final buret reading be if the initial buret reading is 0.77 mL.
Explanation / Answer
Answer: Here the first thing is to be , it is not give the correct end point if we first rapidly add titrant because reaction required same interval of time thats why it is very important to add titrant in a constant manner not rapidly and then after the rest amount .
now the number of moles used to neutralyse a sample is should be in the ration of 1:1 hence the number of moles of NaoH = number of moles of unkwon sample at the end point
and molar mass of unknown sample = 204.44 g/mol
hence number of moles = 0.584 / 204.44 = 0.002856 =
molarity = 0.002856 *1000 / 6.45 = 0.4428 M = M1
hence the estimation of NaOH needed to approach 1 ml = 0.004428 mol
now number of moles of second = 0.934/204.44 = 0.004568
volume required = by using molarity equation we get
= 4.032 ml
Hence the volume of Naoh needed for next trial is 4.032 ml