Question

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 × 103 Jg-1, Specific heat of water = 4.2 Jg-1 °C-1]

Answer 1

The correct answer is 42
$Q = msΔT$
$\frac{dQ}{dt} = (\frac{dm }{dt})_{water}$
$SΔT = (\frac{dm}{dt})_{oil}C$
$⇒ 2 × 4.2 × 10³ × 40$
$= (\frac{dm}{dt})_{oil} × 8 × 10^6$
$⇒ (\frac{dm}{dt})_{oil} = \frac{8 × 4.2 × 10^4}{8 × 10^6} kg/minute$
= 42 g/minute