Tóm tắt:

$V_n = 2\ \text{l} \Rightarrow m_n = 2\ \text{kg}$

$m_{nh} = 200\ \text{g} = 0,2\ \text{kg}$

$t_1 = 20^\circ\text{C}, t_2 = 100^\circ\text{C}$

$c_n = 4200\ \text{J/kg.K}$, $c_{nh} = 880\ \text{J/kg.K}$

$q = 44 \cdot 10^6\ \text{J/kg}$

$H = 30\% = 0,3$

a)

$Q_{ci} = (m_n \cdot c_n + m_{nh} \cdot c_{nh})(t_2 - t_1)$

$Q_{ci} = (2 \cdot 4200 + 0,2 \cdot 880)(100 - 20)$

$Q_{ci} = 686080\ \text{J}$

b) 

$H = \dfrac{Q_{ci}}{Q_{tp}} \Rightarrow Q_{tp} = \dfrac{Q_{ci}}{H} = \dfrac{686080}{0,3} = \dfrac{6860800}{3}\ \text{J}$

$Q_{tp} = m_d \cdot q \Rightarrow m_d = \dfrac{Q_{tp}}{q}$

$m_d = \dfrac{\dfrac{6860800}{3}}{44 \cdot 10^6} \approx 0,052\ \text{kg}$