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Question: Answered & Verified by Expert

A geyser heats water flowing at a rate of 2.0 kg per minute from 30°C to 70°C. If geyser operates on a gas burner, the rate of combustion of fuel will be _____ g min-1.

[Heat of combustion =8×103Jg-1, Specific heat of water =4.2Jg-1C-1]

PhysicsThermal Properties of MatterJEE MainJEE Main 2022 (26 Jun Shift 2)
Solution:
1250 Upvotes Verified Answer
The correct answer is: 42

Given here, mass flow rate of water, dmdt=2 kg min-1

The geyser heats the water, raising the temperature from θ1=30°C to θ2=70°C.

Total heat utilised in raising the temperature, ΔQΔt=dmdt×sΔθ

ΔQΔt=260×4.2×40=mt×L

L= heat of combination=8×103 J g-1

Now, rate of consumption of fuel is mt=2×4.2×4060×8×103

=4.26×10-3=0.7×10-3 kg sec-1

=42 g min-1

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