The Grass Doctor

Okay, I have a Calorimetry problem for homework, help?

In a chemistry experiment, 10g of fertilizer urea, NH2CONH2(s), is dissolved in 150ml of water in a simple calorimeter. A temperature change from 20.4 degrees C to 16.7 degrees C is measured. Calculate the specific heat of solution for urea.

Public Comments

1. well the temperature went down from 20.4-16.7, change of 3.7 3.7x150 = 555 calories was used up to change it from solid to aq 1 mole of urea weight 60g, u had 10, so 555x6=3330 calories/mole for it to turn from solid to liquid
2. Q = m Cp dT if we assume Cp solution = Cp water = 4.184 J/gC m = 150 mL x (1g / mL) + 10 g = 160 g dT = 20.4 - 16.7 = 3.7 C Q = 160 g x 4.184 J/gC x 3.7 C = 2477 J and since mw urea = 60.07 10 g urea x (1 mole / 60.07 g) = 0.116 moles and specific heat of solution = 2477 J / 0.116 moles = 14.9 kJ/mole