C) Lab Related Questions: (Total points 22) C-1 sodium chloride (Na Cl). You are
ID: 560792 • Letter: C
Question
C) Lab Related Questions: (Total points 22) C-1 sodium chloride (Na Cl). You are working in a chemistry lab a customer comes with an aqueous sample of (8 points) su eta c. Please suggest a gravimetric method that it will be suitable to Hint: Use evaporation technique. Start using 10.0 ml of sample and report recovery using the following numbers, by Gravimetric method. Mass of empty evaporating dish is 58.965 g Adding 10 mL of sample increased to 69.987 g After complete dryings came to report the mass percent of Na Cl in this sample. 61.065 g (2 points) (2 points) Answer: a) Find out the mass of sample used in grams. b) % Recovery. c) What is difference between % recovery and % yield? (4points)Explanation / Answer
Ans. #a. Mass of sample used = (Mass of empty evaporating dish + 10 ml solution)) –
(Mass of empty evaporating dish)
= 69.987 g – 58.965 g
= 11.022 g
#b. Mass of NaCl recovered = (Mass of evaporating dish after drying) –
(Mass of empty evaporating dish)
= 60.065 g – 58.965 g
= 2.10 g
% NaCl recovery = (Mass of NaCl recovered / Mass of solution) x 100
= (2.10 g / 11.022 g) x 100
= 19.05 %
#C. % recovery is the amount of specified solute recovered per 100 mL of the solution.
% recovery is also defined as the the amount of specified solute recovered per 100 gram of the same solute in solvated form. However, since the amount of NaCl actually present in 10.0 mL solution is not mentioned, this definition can’t be applied here.
# % Yield is the experimental/ actual amount of product obtained per 100.0 g of theoretical mass produced during the same reaction.
% yield = (Actual yield / Theoretical yield) x 100
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