PRE-LAB or POST-LAB QUIZ Name Instructor/Section Experiment 14: PRE-LAB or POST-

Question

PRE-LAB or POST-LAB QUIZ Name Instructor/Section Experiment 14: PRE-LAB or POST-LAB QUIZ Multiple choice questions. Circle your answers. 1. When the aluminum foil sample and potassium hydroxide are heated on the hot plate, potassium continue heating until the aluminum dissolves and the solution a. boils down to one-fourth the original volume. b. boils down to one-half the original volume. c. boils down to three-fourths the original volume. d. boils completely dry ulate the theoretical yield of alum that can be produced by using 1.08 g of alu- m, Al, using the information given here. (The molar mass of alum is 474 g/mol) l mol Al1 mol alum 27.0 g AI '' I mol Al 474 g alum mole alum mass of alum mass of Al × - Answer 3. Calculate the percentage yield of alum if 16.4 g of alum crystals formed when the theoretical yield was 19.7 g. mass of alum produced x100% = % yield- theoretical yield

Explanation / Answer

Ans 1

On heating

Al(s) + 3 KOH(aq) = Al(OH)3(s) + 3K(s)

After heating products will obtain in solid state.

Boils completely dry.

Option D is the correct answer

Ans 2

Theoretical yield of Alum = 1.08 x 474/27 = 18.96 g

Ans 3

% yield = 16.4*100/19.7

= 83.25 %

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