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

Molecular Formula

General Chemistry

3. Chemical Reactions

Molecular Formula

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Multiple Choice

A gaseous hydrogen and carbon-containing compound is decomposed and found to contain 82.66% carbon and 17.34% hydrogen by mass. The mass of 158 mL of the gas, measured at 556 mmHg and 25 °C, was found to be 0.275 g. What is the molecular formula of the compound?

C2H4

C3H6

C5H10

C4H8

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Verified step by step guidance

Step 1: Begin by determining the empirical formula of the compound. Use the given percentages to find the moles of carbon and hydrogen. Assume a 100 g sample, which means you have 82.66 g of carbon and 17.34 g of hydrogen.

Step 2: Convert the masses to moles using the molar masses of carbon (12.01 g/mol) and hydrogen (1.008 g/mol). Calculate the moles of carbon: \( \text{moles of C} = \frac{82.66 \text{ g}}{12.01 \text{ g/mol}} \). Calculate the moles of hydrogen: \( \text{moles of H} = \frac{17.34 \text{ g}}{1.008 \text{ g/mol}} \).

Step 3: Determine the simplest whole number ratio of moles of carbon to moles of hydrogen to find the empirical formula. Divide the moles of each element by the smallest number of moles calculated in Step 2.

Step 4: Calculate the molar mass of the gas using the ideal gas law. First, convert the pressure from mmHg to atm: \( P = \frac{556 \text{ mmHg}}{760 \text{ mmHg/atm}} \). Use the ideal gas law equation \( PV = nRT \) to find the number of moles \( n \), where \( R = 0.0821 \text{ L atm/mol K} \) and \( T = 25 + 273.15 \text{ K} \).

Step 5: Compare the molar mass obtained from the ideal gas law with the empirical formula mass. Multiply the empirical formula by an integer to match the molar mass calculated, thus determining the molecular formula of the compound.