In Part 2 of Lab #12 you will dissolve about 3 g of urea in 50.0 mL of water and

Question

In Part 2 of Lab #12 you will dissolve about 3 g of urea in 50.0 mL of water and use the change in temperature to determine DeltaH^degreeso|n. Let's go through the calculations. Suppose you dissolve 4.64 g of a solid in 50.0 mL of water. You note that the temperature changes from 25.0 degreeC to 28.2 degreeC. What is the mass of the solution? Assume the density of water is 1.000 g/mL. 54.6 g What is the specific heat capacity of the solution? Determine the absolute value of the change in temperature of the solution. 3.2degreeC 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. -7.3X_102 J If the solid has a molar mass of 86.9 g/mol, determine AHdegree so|n for the solid. Report your answer with the proper sign.

Explanation / Answer

Lets convert 3 g urea into its moles

Number of moles = weight/molar mass = (3 g) / (86.9 g/mol) = 0.0345 moles

The heat involved for 0.0345 moles of urea is -731 J

For 1 mole of urea = (1/0.0345) * (-731) = -21174.63 J/mol = -21.17 kJ/mol

So, Ho = -21.17 kJ/mol

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