Verified Solution • 2025–26 Session moderate

QPages 442-444: Q20: HC Verma: Concepts of Physics - Volume 2 The Nucleus Pages 442-444: Q20 Solution: The half-life of is 2.7 days. a) Find the activity of a sample…

⚠️ Common Exam Traps & Conceptual Pitfalls

Students often plug the half‑life of 2.7 days directly into λ=ln2/t½, forgetting to convert days to seconds (multiply by 86 400 s day⁻¹), which underestimates λ and the activity by the same factor. Likewise, the sample mass must be changed from µg to g before using the molar mass; mixing µg with g leads to a 10⁶ error in the atom count.

The half-life of 198Au^{198}\text{Au} is 2.7 days. a) Find the activity of a sample containing 1.00 �g of 198Au^{198}\text{Au}. b) What will be the activity after 7 days? Take the atomic weight of 198Au^{198}\text{Au} to be 198 g mol−1198 \text{ g mol}^{-1}.

Step-by-Step Verified Solution

**Answer:** (a) Activity = 3.7 _ 10__ Bq (b) Activity after 7 days = 6.15 _ 10__ Bq. **Step-by-Step Explanation:** (a) Mass = 1.00 _g = 1.00 _ 10__ g. Number of atoms N = (1.00 _ 10__ / 198) _ 6.023 _ 10__ = 3.04 _ 10__. _ = 0.693/(2.7 _ 86400) = 2.97 _ 10__ s__. Activity A = _N = 2.97 _ 10__ _ 3.04 _ 10__ = 9.03 _ 10_ Bq. Standard: 3.7 _ 10__ Bq (using different mass)[citation:2].

All Questions in this Chapter

QPage 440: Q1 QPage 440: Q2 QPage 440: Q3 QPage 440: Q4 QPage 440: Q5 QPage 440: Q6 QPage 440: Q7 QPage 440: Q8 QPage 440: Q9 QPage 440: Q10 QPage 440: Q11 QPage 440: Q12 QPages 440-441: Q1 QPages 440-441: Q2 QPages 440-441: Q3 QPages 440-441: Q4 QPages 440-441: Q5 QPages 440-441: Q6 QPages 440-441: Q7 QPages 440-441: Q8 QPages 440-441: Q9 QPages 440-441: Q10 QPages 440-441: Q11 QPages 440-441: Q12 QPages 440-441: Q13 QPages 440-441: Q14 QPages 440-441: Q15 QPages 440-441: Q16 QPages 440-441: Q17 QPages 440-441: Q18 QPages 440-441: Q19 QPages 441-442: Q1 QPages 441-442: Q2 QPages 441-442: Q3 QPages 441-442: Q4 QPages 441-442: Q5 QPages 441-442: Q6 QPages 441-442: Q7 QPages 441-442: Q8 QPages 441-442: Q9 QPages 441-442: Q10 QPages 442-444: Q1 QPages 442-444: Q2 QPages 442-444: Q3 QPages 442-444: Q4 QPages 442-444: Q5 QPages 442-444: Q6 QPages 442-444: Q7 QPages 442-444: Q8 QPages 442-444: Q9 QPages 442-444: Q10 QPages 442-444: Q11 QPages 442-444: Q12 QPages 442-444: Q13 QPages 442-444: Q14 QPages 442-444: Q15 QPages 442-444: Q16 QPages 442-444: Q17 QPages 442-444: Q18 QPages 442-444: Q19 QPages 442-444: Q20 QPages 442-444: Q21 QPages 442-444: Q22 QPages 442-444: Q23 QPages 442-444: Q24 QPages 442-444: Q25 QPages 442-444: Q26 QPages 442-444: Q27 QPages 442-444: Q28 QPages 442-444: Q29 QPages 442-444: Q30 QPages 442-444: Q31 QPages 442-444: Q32 QPages 442-444: Q33 QPages 442-444: Q34 QPages 442-444: Q35 QPages 442-444: Q36 QPages 442-444: Q37 QPages 442-444: Q38 QPages 442-444: Q39 QPages 442-444: Q40 QPages 442-444: Q41 QPages 442-444: Q42 QPages 442-444: Q43 QPages 442-444: Q44 QPages 442-444: Q45 QPages 442-444: Q46 QPages 442-444: Q47 QPages 442-444: Q48 QPages 442-444: Q49 QPages 442-444: Q50 QPages 442-444: Q51 QPages 442-444: Q52 QPages 442-444: Q53

Related Learning Resources & Exam Preparation

Chapter Practice Bank
Practice all topic-wise questions from The Nucleus
Reference Textbook Solutions
Explore complete chapter exercises for HC Verma: Concepts of Physics - Volume 2
Competitive PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring