Heat that needed

jack1234

For this question:
http://tinyurl.com/2leprw

Followed is my working

Q=m_w*c_w*deltaT + m_w*L_f + m_w*c_i*deltaT
=m_w[
c_w*deltaT +
L_f +
c_i*deltaT
]
=2*(10^3)g [
1 cal/(g*celcius) * 20 celcius +
(3.33*(10^5)*0.2389/1000)calories/g +
0.5 cal/(g*celcius) * 10 celcius
]
=209100J

And this is not one of the choices...
Can anybody kindly pointed out what is my mistake?

Astronuc

Well the choice of answers are in kcal rather than J.

Q=m_w*c_w*deltaT + m_w*L_f + m_w*c_i*deltaT

is correct. M = 2000 g (2 kg) so

Q = 2000 g ( c_w*c_w*deltaT + L_f + c_i*deltaT)

= 2000 g ( 1 cal/(g-°C) * 20°C + 79.7 cal/g + 0.5 (cal/g°C) * 10°C)

Be careful with conversions, and please show units.

Kurdt

Using the values you've given even I don't get an answer thats on the sheet.