l. Percent Composition 1. Given the table below, calculate the number of student

Question

l. Percent Composition 1. Given the table below, calculate the number of students wearing purple in the class. Measurement of Students and color shirt Color Red Blue Yellow Purple No. students 32 56 48 18 a. How do you calculate the percent students wearing purple? b, the percent wearing purple = 2. calculating the percent composition in a compound is much the same as the exercise above. Consider the compound caffeine, CH0N402 What is the formula weight? What is the total mass of carbon? The percent carbon is calculated according to the following formula a. b. c.

Explanation / Answer

II. percent composition

1. Color precent

a. Total students = 32 + 56 + 48 + 18 = 154

percent purple = (number of student with purple shirt/total students) x 100

b. percent students with purple shirt = (18/154) x 100 = 11.7%

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2. formula = C8H10N4O2

a. formula weight = 12 x 8 + 10 x 1 + 14 x 4 + 16 x 2 = 194

b. mass carbon = 12 x 8 = 96

c. percent carbon = (mass carbon/total mass) x 100

d. mass percent carbon = (96/194) x 100 = 49.5%

f. mass percent H = (10/194) x 100 = 5.1%

g. mass percent N = (56/194) x 100 = 28.9%

h. mass percent O = (32/194) x 100 = 16.5%

i. total percent = 100%

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3. Ibuprofen formula C13H18O2

formula weight = 13 x 12 + 18 x 1 + 16 x 2 = 206

mass percent oxygen = (32/206) x 100 = 15.53%

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4. formula = (NH4)2S

formula weight = [2 x (14 + 4 x 1)] + 32 = 68

mass percent hydrogen = (8/68) x 100 = 11.8%

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