Question

How many kilocalories are required to increase the temperature of 15.6 g of iron from 122 °C to 355 °C? The specific heat of iron is 0.450 J/g· °C.

Answer 1

Ans. Amount of heat change required is given by-

            q = m s dT                            - equation 1

Where,

q = heat change required

m = mass

s = specific heat

dT = Final temperature – Initial temperature = (T2 – T1)⁰C

Given, specific heat of iron = 0.450 J g^-10C^-1                                           ; [1 Cal = 4.184 J]

                                                = [0.450 x (1 / 4.184)] Cal g^-10C^-1

                                                = 0.107553 Cal g^-10C^-1

Temperature change, dT = 355.0⁰C – 122.0⁰C = 233.0⁰C

Now,

            Putting the values in equation 1-

            q = 15.6 g x (0.107553 Cal g^-10C^-1) x 233.0⁰C

            Or, q = 390.9336 Cal

Hence amount of heat required = 390.9336 Cal                                     ; [1 kCal = 10³ Cal]

                                                = 0.391 kCal