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

7. Gases

The Ideal Gas Law: Molar Mass

General Chemistry

7. Gases

The Ideal Gas Law: Molar Mass

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Multiple Choice

What is the molecular formula of a compound that contains 39.0% carbon, 16.0% hydrogen, and 45.0% nitrogen, if 0.1576 g of the compound occupies 125 mL with a pressure of 0.9820 atm at 295.15 K?

CH₃N

CH₅N

C₂H₃N₂

C₂H₅N₂

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Verified step by step guidance

First, convert the percentage composition of each element to grams, assuming you have 100 g of the compound. This means you have 39.0 g of carbon, 16.0 g of hydrogen, and 45.0 g of nitrogen.

Next, convert the mass of each element to moles by dividing by their respective molar masses: Carbon (C) is 12.01 g/mol, Hydrogen (H) is 1.008 g/mol, and Nitrogen (N) is 14.01 g/mol.

Determine the simplest whole number ratio of moles of each element by dividing each by the smallest number of moles calculated in the previous step.

Use the ideal gas law, PV = nRT, to find the number of moles of the compound. Here, P is the pressure (0.9820 atm), V is the volume (0.125 L), R is the ideal gas constant (0.0821 L·atm/mol·K), and T is the temperature (295.15 K). Solve for n, the number of moles.

Finally, use the number of moles calculated from the ideal gas law and the mass of the compound (0.1576 g) to find the molar mass. Compare this molar mass with the empirical formula mass to determine the molecular formula.