Question

The amount of steam at ${100}^{0}c$ required to raise the temperature of 200 g of water from ${60}^{0}c$ to ${100}^{0}c$ is (for steam at ${100}^{0}c$ $h_{fg}=2257kJ/kg$

• A. 14.8 kg
• B. 14.8 g
• C. 19.8 g
• D. 19.8 Kg

Answer 1

The correct option is B 14.8 g

$m_{\omega }=200g$ = 0.2 Kg

$C_{\omega }$ = 4.187 kJ/kgK

$h_{fg}=2257kJ/kg$

From energy balance

$m_s\times h_{fg}=m_{\omega }{C}_{\omega }(T_2-T_1)$

$m_s\times 2257=0.2\times 4.187(100-60)$
$m_s=14.8\times {10}^{-3}kg=14.8g$