WAEC Physics 2025 Theory — Question 27
Question 27 of 34 from the West African Examinations Council (WAEC) Physics 2025 Theory paper, with the correct answer and a full explanation.
Advertisement
12(c)(i) Given that ¹³₇G undergoes alpha decay: I. Write an equation representing the process. II. Identify the daughter nuclide. (ii) In the decay series ²³⁸U → ²⁰⁶Pb + n(⁴₂He), determine the number of alpha particles emitted.
Model answer
(i) I. ¹³₇G → ⁴₂He + ⁹₅Y. II. Daughter nuclide has mass number 9 and atomic number 5 (as given in the WAEC marking scheme). (ii) By conservation of mass number: 238 = 206 + 4n → 4n = 32 → n = 8. Therefore, eight (8) alpha particles are emitted in the decay series.
Advertisement
Sign up free to unlock
- Score tracking
- Practice history
- Saved questions
- Progress dashboard
- Personalized sessions
- Weak-topic breakdown
…and/or go further with premium services and No Ads.