Question 43
Quantity of HeatA calorimeter of thermal capacity 80 J contains 20 g of water at 25°C. Water at 100°C is added so that the final temperature of the set-up is 50°C. The amount of water added is (Heat capacity of water = 4.18 J/g/°C)
- A.20 g
- B.25 g
- C.45 g
- D.50 g
- E.100 g.
Show the answer and explanation
Answer: A (20 g)
Explanation
Heat lost by hot water = heat gained: m × 4.18 × 50 = 80 × 25 + 20 × 4.18 × 25 = 2000 + 2090. So 209m = 4090 and m ≈ 20 g.