Post-Laboratory Questions (use the spaces provided for the answers and additiona
ID: 500842 • Letter: P
Question
Post-Laboratory Questions (use the spaces provided for the answers and additional paper ifnecessary) 1. Which of the antacids investigated by your laboratory section is most cost effective? 2. A Brand X antacid tablet was analyzed by a student following the procedure used in this experiment. The student dissolved the tablet in 25.00 HCI solution containing 1627 x 10 mol of HCI. The back-titration of the excess HCI required 7.83 ml of 1.035M NaoH solution. (a) Calculate the molar concentration of the HCI solution that the student used. (b) Calculate the number of moles of HCI tralized by the antacid tabletExplanation / Answer
Number of moles of HCl neutralize per tablet :
Determination 1 : 0.015-0.004 =0.011 moles
Deternimation 2 : 0.015-0.004 = 0.011 moles
Determination 3 : 0.015-0.0038 =0.0112 moles
Average = 0.011 moles
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Number of moles of HCl neutralize per gram of tablet
Determination 1 : 0.011 moles/ 2.6 gm = 4.23*10^-3 moles
Deternimation 2 : 0.011 moles/2.6457 gm = 4.16*10^-3 moles
Determination 3 : 0.0112 moles/2.6730 gm = 4.19*10^-3 moles
average = 4.19*10^-3 moles/gram
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Mass effectiveness = 4.19*10^-3 moles/gram
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cost of one tablet = 6.29/72 = $ 0.087
cost effectiveness = 0.011moles/$ 0.087 =0.126
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Pre-laboratory assignment
1.Both HCl and NaOH are corrosive to skin . It can react with the organic material present on the skin causing severe burning. So, if you spill HCl or NaOH on skin, you should immediately wash it.
2. (a) Antacid is basic in nature. When you add HCl to it, some of the antacid will be neutralize and there will be some extra HCl present.
(b) The extra HCl in the previous step is neutralize by NaOH. this is called back titration
(c) amount of stomach acid that can be neutralize by the antacid is its cost effectiveness.
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3. At the end point of back titration there will be a color change by the indicator. If you are using phenophthalein indicator, this point will be colorless to pink color change