Ch.3 - Chemical ReactionsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: An organic compound contains C, H, and O. The percentages of H and C are 6.73% H, and 39.99% C by mass. The molar mass is 60.06 amu. What is the molecular formula of the compound?A) CH2OB) C4H8O4C) C2

Solution: An organic compound contains C, H, and O. The percentages of H and C are 6.73% H, and 39.99% C by mass. The molar mass is 60.06 amu. What is the molecular formula of the compound?A) CH2OB) C4H8O4C) C2

Problem

An organic compound contains C, H, and O. The percentages of H and C are 6.73% H, and 39.99% C by mass. The molar mass is 60.06 amu. What is the molecular formula of the compound?

A) CH2O

B) C4H8O4

C) C2H3O2

D) C2H4O2

E) C3H6O3

Solution

We’re being asked to determine the molecular formula of a compound composed of C, H, and O given the mass percent of C and H. This means we need to do the following steps:


Step 1: Calculate the mass and moles of C, H, and O in the compound.

Step 2: Determine the lowest whole number ratio of C, H, and O to get the empirical formula.

Step 3: Get the ratio of the molar mass and empirical mass to determine the molecular formula.


Step 1: The compound is composed of C, H, O and we’re only given the mass percent of C (39.99% C) and H (6.73% H). Recall that the mass percentages of a compound must add up to 100%. This means:



Recall that mass percent is given by:



Assuming we have 100 g of the compound, this means we have 39.99 g C, 6.73 g H, and 53.28 g O. Now, we need to get the moles of each element in the compound. The atomic masses are 12 g/mol C, 1 g/mol H, 16 g/mol O.


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