Question

Calculate the amount of heat needed to boil 183.g of ethanol ( CH3CH2OH ), beginning from a temperature of 33.9°C . Round your answer to 3 significant digits. Also, be sure your answer contains a unit symbol.

Answer 1

Sol :-

Q = m x c x dT

mass of ethanol = 183 g

heat capacity of ethanol = 2.238 J g^-1 K^-1

dT = Change in temperature = T_f - T_i = 78.3 ⁰C (B.P of ethanol) - 33.9 ⁰C = 44.4 ⁰C or 44.4 K

= 183 g x 2.238 J g^-1 K^-1 x 44.4 K

= 18184.1976 J

= 18.2 KJ

= 18.2 KJ

Moles of ethanol = 183 g/ 46 g/ moles

= 3.98 mol

Now heat of vaporization = 38.56 KJ/ mol x  number of moles

= 38.56 KJ/ mol x  3.98 mol

= 153.5 KJ

Total heat = 18.2 KJ + 153.5 KJ

= 171.7 KJ

Hence, Total heat needed = 171.7 KJ