Question

The specific heat capacity of S8 (s), at 25 C is 5.430 cal.K -1 . g -1 . A) what is the molar heat capacity of S8 in J.K-1.mol-1 at this temperature? hint: 1 cal = 4.184 J. B) 500.0 g sample of S8 at 25.0 C absorbs 50.00 kj of energy. what will be the final temperature of the sample in C? I dont need just the answer, I got this question wrong and I need to know how to do it.

Answer 1

specific heat capacity is given in grams which should be converted to 1 mole

Molar mass of S8 = 256.48 g/mol

molar heat capacity in calories = 5.43 x 256.48 = 1392.6864 Calories

let us convert calories to joules

1 calorie = 4.184 Joules

1392.6864 Calories = 5827 Joules

molar heat capacity of S8 = 5827 J.K-1.mol-1

Q = mc∆T

Q = heat energy (Joules, J), m = mass of a substance (kg)

c = specific heat (units J/kg∙K), ∆ is a symbol meaning "the change in"

∆T = change in temperature (Kelvins, K)

5.43 calories = 22.71912 Jouels

50000 = 500 x 22.71912 x (Tf-25)

Tf = 69.01 Deg celcius

Hence the final temperature is  69.01 Deg celcius