Practice question
Question
A 0.45kg copper block at 200∘C is placed in 1.1kg water at 23∘C in a 0.2kg brass calorimeter at 23∘C. What is the final temperature? (Specific heat of copper = 386J kg−1K−1, water = 4186J kg−1K−1, brass = 386J kg−1K−1)
Explanation
Heat lost = Heat gained. 0.45×386×(200−T) = (1.1×4186+0.2×386)×(T−23). 34740−173.7T = (4604.6+77.2)×(T−23) = 4681.8T−107678.4. 34740+107678.4 = 4681.8T+173.7T. 142418.4 = 4855.5T⇒T≈29.33∘C≈29.3∘C. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 29.3°C. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.
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