Practice question
Question
A 0.2kg tungsten block at 250∘C is dropped into 0.5kg water at 18∘C in a 0.1kg silver calorimeter at 18∘C. What is the final temperature? (Specific heat of tungsten = 134J kg−1K−1, water = 4186J kg−1K−1, silver = 236Jkg−1K−1)
Explanation
0.2×134×(250−T) = (0.5×4186+0.1×236)×(T−18). 6700−26.8T = (2093+23.6)×(T−18) = 2116.6T−38098.8. 6700+38098.8 = 2116.6T+26.8T. 44798.8 = 2143.4T⇒T≈20.9∘C. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 20.9°C. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
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