Question

In Part 2 of Lab 5 you will dissolve about 3 g of urea in 50.0 mL of water and use the change in temperature to determine Delta H degree_soln. Let's go through the calculations. Suppose you dissolve 4.72 g of a solid in 50.0 mL of water. You note that the temperature changes from 25.0 degree C to 28.3 degree C. What is the mass of the solution? Assume the density of water is 1.000 g/mL. g What is the specific heat capacity of the solution? J/g degree C Determine the absolute value of the change in temperature of the solution. degree c Determine the total heat involved in dissolving your samples of the solid in 50.0 mL of water. Report your answer with the proper sign. J If the solid has a molar mass of 91.7 g/mol, determine Delta H degree_soln for the solid. Report your answer with the proper sign.

Answer 1

P1:

mass of solution

mass of water = 1 g/mL * 50 mL = 50 g

total mass of solution = 4.72+50 = 54.72 g

P2.

Assume that the specific heat of the mix is equal to that of water, i.e. 4,184 J/gK

P3.

Absolute value of chang ein temperature:

Tf-Ti = 28.3-25.0 = 3.3 °C

P4.

Total heat involved

Q = m*C*(Tf-Ti)

Q = 54.72*4.184*3.3 = 755.529 J