Question

The equivalent weight of a solid element is found to be 9. If
the specific heat of this element is 1.05 Jg⁻¹ K⁻¹, then its
atomic weight is :
(a) 17 (b) 21 (c) 25 (d) 27

Answer 1

Atomic weight of the element is 27

Explanation:

Valency of the element is the ratio in between the approximate atomic weight to the equivalent weight.

• According to DULONG & PETIT's method,
• $Specific\,heat\times Atomic\,weight =6.4$
• Given that, specific heat of the element $=1.05Jg^{-1}K^{-1}$
• But, specific heat should be taken in calories gram/degree
• Therefore, specific heat $=1.05 J/gK=1.05/4.18 calories \,gram/degree=0.25 cal\, g/d$
• Hence, $0.25 \times approx\, atomic\,weight = 6.4$
• Therefore, Approx atomic weight = 25.6
• $Valency = \frac{Approx \, atomic \, weight}{Equivalent \, weight}$  
• $=\frac{25.6}{9} =2.84 \approx 3$     ($\because$ Valency should be a whole number)
• $Atomic \, weight = valence \times equivalent \, weight$  
• $3 \times 9 =27$  

Therefore, the correct answer is option (d)

Answer 2

Answer:

ovation D, 27 this answer is perfect