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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

21. Nuclear Chemistry

Rate of Radioactive Decay

General Chemistry

21. Nuclear Chemistry

Rate of Radioactive Decay

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Multiple Choice

A sample of Th-219 requires 3.84 × 10⁻⁶ seconds to decay to 1.50 mg. What was the initial mass of the sample of Th-219? (t_1/2 for Th-219 = 1.05 × 10⁻⁶ s)

3.00 mg

5.90 mg

18.9 mg

37.8 mg

56.1 mg

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Identify the given values: the final mass of Th-219 is 1.50 mg, the time taken for decay is 3.84 × 10^(-6) seconds, and the half-life (t1/2) of Th-219 is 1.05 × 10^(-6) seconds.

Use the formula for radioactive decay: N = N0 * (1/2)^(t/t1/2), where N is the final mass, N0 is the initial mass, t is the time elapsed, and t1/2 is the half-life.

Rearrange the formula to solve for the initial mass (N0): N0 = N / (1/2)^(t/t1/2).

Substitute the known values into the rearranged formula: N0 = 1.50 mg / (1/2)^(3.84 × 10^(-6) s / 1.05 × 10^(-6) s).

Calculate the exponent (t/t1/2) and then evaluate the expression to find the initial mass N0.

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Struggling with General Chemistry?

A sample of Th-219 requires 3.84 × 10−6 seconds to decay to 1.50 mg. What was the initial mass of the sample of Th-219? (t1/2 for Th-219 = 1.05 × 10−6 s)

Watch next

Rate of Radioactive Decay practice set

A sample of Th-219 requires 3.84 × 10⁻⁶ seconds to decay to 1.50 mg. What was the initial mass of the sample of Th-219? (t_1/2 for Th-219 = 1.05 × 10⁻⁶ s)