Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

3. Chemical Reactions

Empirical Formula

General Chemistry

3. Chemical Reactions

Empirical Formula

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Multiple Choice

An unknown compound contains only carbon, hydrogen, and oxygen. Using combustion analysis, you burned 19.31 mg of the sample and collected 17.96 mg of H2O and 43.89 mg of CO2. What is the empirical formula of this compound?

C2H6O

C3H6O

C2H4O

C3H8O

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Verified step by step guidance

Start by determining the moles of carbon in the CO2 produced. Use the molar mass of CO2 (44.01 g/mol) to convert the mass of CO2 to moles: \( \text{moles of CO2} = \frac{43.89 \text{ mg}}{44.01 \text{ g/mol}} \). Since each mole of CO2 contains one mole of carbon, the moles of carbon will be the same as the moles of CO2.

Next, calculate the moles of hydrogen in the H2O produced. Use the molar mass of H2O (18.02 g/mol) to convert the mass of H2O to moles: \( \text{moles of H2O} = \frac{17.96 \text{ mg}}{18.02 \text{ g/mol}} \). Since each mole of H2O contains two moles of hydrogen, multiply the moles of H2O by 2 to find the moles of hydrogen.

Determine the mass of carbon and hydrogen in the original sample using their respective moles and atomic masses (carbon: 12.01 g/mol, hydrogen: 1.008 g/mol). Calculate the mass of carbon: \( \text{mass of carbon} = \text{moles of carbon} \times 12.01 \text{ g/mol} \) and the mass of hydrogen: \( \text{mass of hydrogen} = \text{moles of hydrogen} \times 1.008 \text{ g/mol} \).

Find the mass of oxygen in the sample by subtracting the mass of carbon and hydrogen from the total mass of the sample: \( \text{mass of oxygen} = 19.31 \text{ mg} - (\text{mass of carbon} + \text{mass of hydrogen}) \). Convert this mass to moles using the molar mass of oxygen (16.00 g/mol): \( \text{moles of oxygen} = \frac{\text{mass of oxygen}}{16.00 \text{ g/mol}} \).

Determine the empirical formula by finding the simplest whole number ratio of moles of carbon, hydrogen, and oxygen. Divide the moles of each element by the smallest number of moles calculated in the previous steps. Adjust the ratios to the nearest whole numbers to find the empirical formula.