Question

70kg of Masa is heated from -24.0c to 85.0c . Her M.p is 10.0c and her boiling point us 95.oC . How much energy did she lose ? Csolid=1500j/kgC , Cliquid =3800j/kgc Cgas =2100 J/KgC Lf 56000J/kg Lv=20000j/kg
Can you please help me answering this question ? Thank you

Answer 1

Question#19513

70kg of Masa is heated from -24.0c to 85.0c. Her M.p is 10.0c and her boiling point us 95.oC. How much energy did she lose? Csolid=1500j/kgC, Cliquid =3800j/kgc Cgas =2100 J/KgC Lf 56000J/kg Lv=20000j/kg

Can you please help me answering this question? Thank you

Solution:

Let:

$$m = 70 \text{ kg}$$ $$T_1 = -24^\circ\text{C}$$ $$T_2 = 85^\circ\text{C}$$ $$T_f = 10^\circ\text{C}$$ $$c_e = 1500 \text{ j/kg}^\circ\text{C}$$ $$c_i = 3800 \text{ j/kg}^\circ\text{C}$$ $$L_f = 2100 \text{ j/kg}^\circ\text{C}$$

Q - ?

$$Q = Q_e + Q_f + Q_i, \quad \text{were: } Q_e - \text{energy needed to heated solid}, \\ Q_f - \text{energy needed to fusion}, \quad Q_i - \text{energy needed to heated liquid}$$ $$Q = m c_e \Delta T + m L_f + m c_i \Delta T$$ $$Q = 70 * 1500(10 - (-24)) + 70 * 2100 + 70 * 3800(85 - 10) = 23667 \text{ kJ}$$

Answer: 23667 KJ.