1. Matter and Measurements4h 29m
2. Atoms and the Periodic Table5h 23m
3. Ionic Compounds2h 18m
4. Molecular Compounds2h 18m
5. Classification & Balancing of Chemical Reactions3h 17m
6. Chemical Reactions & Quantities2h 35m
7. Energy, Rate and Equilibrium3h 46m
8. Gases, Liquids and Solids3h 25m
9. Solutions4h 10m
10. Acids and Bases3h 29m
11. Nuclear Chemistry56m
BONUS: Lab Techniques and Procedures1h 38m
BONUS: Mathematical Operations and Functions47m
12. Introduction to Organic Chemistry1h 34m
13. Alkenes, Alkynes, and Aromatic Compounds2h 12m
14. Compounds with Oxygen or Sulfur1h 6m
15. Aldehydes and Ketones1h 1m
16. Carboxylic Acids and Their Derivatives1h 11m
17. Amines38m
18. Amino Acids and Proteins1h 51m
19. Enzymes1h 37m
20. Carbohydrates1h 46m
21. The Generation of Biochemical Energy2h 8m
22. Carbohydrate Metabolism2h 22m
23. Lipids2h 26m
24. Lipid Metabolism1h 45m
25. Protein and Amino Acid Metabolism1h 37m
26. Nucleic Acids and Protein Synthesis2h 54m

8. Gases, Liquids and Solids

Standard Temperature and Pressure

GOB Chemistry

8. Gases, Liquids and Solids

Standard Temperature and Pressure

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3:56 minutes

Problem 78McMurry - 8th Edition

Textbook Question

Which sample contains more molecules: 2.0 L of Cl₂ at STP or 3.0 L of CH₄ at 300 K and 1150 mmHg? Which sample weighs more?

Verified step by step guidance

Identify the conditions for each gas sample: Cl₂ is at STP (Standard Temperature and Pressure), which is 0°C (273.15 K) and 1 atm (760 mmHg), while CH₄ is at 300 K and 1150 mmHg.

Use the ideal gas law, PV = nRT, to calculate the number of moles (n) for each gas. For Cl₂ at STP, use the molar volume of a gas at STP, which is 22.4 L/mol, to find the moles. For CH₄, rearrange the ideal gas law to n = PV/RT and substitute the given values (P = 1150 mmHg, V = 3.0 L, R = 62.36 L mmHg/mol K, T = 300 K) to find the moles.

Compare the number of moles of Cl₂ and CH₄ to determine which sample contains more molecules, using Avogadro's number (6.022 × 10²³ molecules/mol) to convert moles to molecules if needed.

Calculate the mass of each gas sample. For Cl₂, use the molar mass of Cl₂ (approximately 70.9 g/mol) and multiply by the number of moles calculated. For CH₄, use the molar mass of CH₄ (approximately 16.04 g/mol) and multiply by the number of moles calculated.

Compare the masses of Cl₂ and CH₄ to determine which sample weighs more.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Avogadro's Law

Avogadro's Law states that equal volumes of gases, at the same temperature and pressure, contain an equal number of molecules. This principle is crucial for comparing the number of molecules in different gas samples, as it allows us to determine that 2.0 L of Cl₂ at STP (Standard Temperature and Pressure) contains a specific number of molecules, which can be directly compared to the number of molecules in 3.0 L of CH₄ under different conditions.

Ideal Gas Law

The Ideal Gas Law (PV = nRT) relates the pressure, volume, temperature, and number of moles of a gas. This law is essential for calculating the number of moles of CH₄ in the given conditions (300 K and 1150 mmHg) to determine how many molecules are present. By rearranging the equation, we can solve for 'n' (the number of moles) and subsequently find the number of molecules.

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). To compare the weights of the two gas samples, we need to calculate the mass of each gas using their respective molar masses (Cl₂ = 70.9 g/mol and CH₄ = 16.04 g/mol) and the number of moles derived from the Ideal Gas Law. This allows us to determine which sample weighs more.