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

A 45.2 mg sample of phosphorus reacts with selenium to form 131.6 mg of the selenide. Determine the empirical formula of phosphorus selenide.

P2Se3

PSe

P4Se3

PSe2

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Verified step by step guidance

Convert the mass of phosphorus from milligrams to grams by dividing by 1000. This gives you the mass in grams, which is necessary for calculating moles.

Calculate the moles of phosphorus using its molar mass. The molar mass of phosphorus (P) is approximately 30.97 g/mol. Use the formula: \( \text{moles of P} = \frac{\text{mass of P in grams}}{\text{molar mass of P}} \).

Determine the mass of selenium in the compound by subtracting the mass of phosphorus from the total mass of the selenide. This gives you the mass of selenium in milligrams, which you then convert to grams.

Calculate the moles of selenium using its molar mass. The molar mass of selenium (Se) is approximately 78.96 g/mol. Use the formula: \( \text{moles of Se} = \frac{\text{mass of Se in grams}}{\text{molar mass of Se}} \).

Determine the simplest whole number ratio of moles of phosphorus to moles of selenium by dividing each by the smallest number of moles calculated. This ratio gives you the subscripts for the empirical formula of phosphorus selenide.