Sally weighted out 3 portions of unknown acid into clean Erlenmeyer flasks and e

Question

Sally weighted out 3 portions of unknown acid into clean Erlenmeyer flasks and entered the data into the following table. She then titrated each with her standardized base solution, prepared in Experiment 10, which she calculated to be 0.1044 M.

a. Fill in all the missing data and calculate the molar mass of the unkown acid for each trial.

b. Calculate the average molar mass (X) for Sally's data.

c. Calculate the standard deviation in Sally's data (Y) and report the result as "XY" below.

Molar Mass of Unknown Acid = _________+/-__________

--------------------------------------- Trial 1 Trial 2 Trial 3 Mass of (weighing tray + acid) (g) 9.423 8.580 7.788 Mass after acid removal (g) 8.580 7.788 6.987 Mass of acid removed (g) Molarity of base soln (M) Final buret reading (mL) 26.68 25.67 25.46 Initial buret reading (mL) .73 1.03 .95 Volume of NaOH soln (mL) Moles of NaOH Moles acid Molar Mass Acid

Explanation / Answer

a)

each element Row-wise :->

0.843 , 0.792 , 0.801

0.1044M , 0.1044M , 0.1044M

25.95 , 24.64, 24.51

2.71 , 2.572, 2.558 ( * 10^-3 moles)

2.71 , 2.572, 2.558 ( * 10^-3 moles)

311.07 , 307.93 , 313.135

b) Average Molar mass = 310.712 gm/mol

c)Molar Mass of Unknown = 310.712 +/- 2.621.

Standard Deviation = 2.621 gm/mol

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