EXPERIMENT 5 QUESHOTORYEERN HE BrAEACTN PRE-LABORATORY OF A REACTION NAME DATE 1

Question

EXPERIMENT 5 QUESHOTORYEERN HE BrAEACTN PRE-LABORATORY OF A REACTION NAME DATE 1. What is the molar mass of the potassium alum salt, KAKSO2 12H20 mslar mess oF K:39.098 2. A student used a piece of aluminum that had a mass of 2.583 grams, and treated according to the same procedure you used in this experiment 2 Ads) + 2 KOhHaq) + 4 H2804(aq) + 22H200 2 KAisod2. 12H20 s) + 3H2 How many moles of Al did the student use in this experiment? a. b. How many moles of the Alum, KASO2 12 H20, can be produced theoretically? Hint Use the coefficients from the balanced chemical equation) What is the mass of Alum theoretically possible? (Hint -Use the molar mass of the alum calculated in question #1) c. d. If the student's crystals had a mass of 32.105 g, what is the percent yield? EXPERIMENT5 99

Explanation / Answer

1) molar mass of potash alum = 474.3884 g/mol

2)

a) moles of Al used = 2.583g x 1mol / 24.981g

= 0.1034 mol

b) From the balanced equation

2 moles of Al give 2 moles of alum

Thus

0.1034mol of Al gives 0.1034 moles of alum

c) theoretical mass of alum = theoretical moles x molar mass

= 0.1034 mol x 474.3884 g/mol

= 49.0510g

d)

% yield = experimental yield x 100 / theoretical yield

= 32.105 x 100/ 49.0510

= 65.45%

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