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CHEM103 / CHEM 103 Module 2:

(Latest Update 2025 / 2026) General Chemistry I with Lab | Questions & Answers | Grade A | 100% Correct - Portage Learning

Question:

Show the calculation of the empirical formula for each compound whose elemental composition is shown below.

23.06% Al, 15.40% C, 61.54% O

Answer:

-23.06% Al / 26.98 = 0.8547 / 0.8547 = 1 x 2 = 2

-15.40% C / 12.01 = 1.282 / 0.8547 = 1.5 x 2 = 3

-61.54% O / 16.00 = 3.846 / 0.8547 = 4.5 x 2 = 9 → Al2C3O9

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Question:

Show the calculation of the percent of each element present in the following compounds. Report your answer to 2 places after the decimal.

1. (NH4)2CO3

• C8H6NO4Br

Answer:

• N = 2 x 14.01/96.09 x 100 = 29.16%

H = 8 x 1.008/96.09 x 100 = 8.39% C = 1 x 12.01/96.09 x 100 = 12.50% O = 3 x 16.00/96.09 x 100 = 49.95%

• C = 8 x 12.01/260.04 x 100 = 36.95%

H = 6 x 1.008/260.04 x 100 = 2.33% N = 1 x 14.01/260.04 x 100 = 5.39% O = 4 x 16.00/260.04 x 100 = 24.61% Br = 1 x 79.90/260.04 x 100 = 30.73%

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Question:

Balance each of the following equations by placing coefficients in front of each substance.

1. C2H6 + O2 → CO2 + H2O

• Al + O2 → Al2O3

• Ca + H3PO4 → Ca3(PO4)2 + H2

Answer:

1. 2 C2H6 + 7 O2 → 4 CO2 + 6 H2O

• 4 Al + 3 O2 → 2 Al2O3

• 3 Ca + 2 H3PO4 → Ca3(PO4)2 + 3 H2

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Question:

Classify each of the following reactions as either:

Combination Decomposition Combustion Double Replacement Single Replacement

1. C5H12 + 8 O2 → 5 CO2 + 6 H2O

• Zn + CuSO4 → Cu + ZnSO4

• 2 Fe + 3 Cl2 → 2 FeCl

Answer:

• C5H12 + 8 O2 → 5 CO2 + 6 H2O = Combustion, Hydrocarbon + O2 → CO2
• H2O

• Zn + CuSO4 → Cu + ZnSO4 = Single Replacement, Metal displaces metal

ion

• 2 Fe + 3 Cl2 → 2 FeCl3 = Combination. Two reactants→ One prod

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