Part A: A hypothetical solution forms between a solid and a liquid. The values o

Question

Part A:

A hypothetical solution forms between a solid and a liquid. The values of the thermodynamic quantities involved in the process are shown in the following table.

Calculate the enthalpy of solution in kilojoules per mole of solute.

Enter your answer numerically in kilojoules per mole of solute.

Part B:

A 4.00 m solution of KCl was prepared using 1.00 kg of water at 25.0 C. Once the solid had all dissolved, the temperature of the solution was 12.3 C. Calculate the heat of solution, Hsoln, of KCl. Assume that the specific heat of the solution is identical to that of water, 4.18 J/(gC).

Express your answer numerically in kilojoules per mole.

Action Enthalpy Separation of Solute 17.5 kJ/mol Separation of Solvent 28.8 kJ/mol Formation of Solute-Solvent Interactions -90.7 kJ/mol solute

Explanation / Answer

We know the enthalpy of the solution is given by following equation.

Delta Hsol = Delta H product – Delta Hreactant.

Here product is solute and solvent system,

Reactants : We have to use separation value of solute and solvent together.

Lets plug given value in above equation.

Delta H of solution = ( - 90.7 ) – ( 17.5 + 28.8 )

= -137 kJ / mol

Question 2 :

Given : Temperature change = (12.3 – 25.0 ) deg C

Molarity = 4.0 m

Mass of water = 1.0 kg

Lets first find heat of solution.

q (solution) = m C delta T

here C is specific heat of solution, m is mass of solution in g, Delta T is change in T

q = (mass of water in g + mass of KCl in g ) x 4.184 J / g deg C x (12.3 – 25.0 ) deg C

Lets calculate mass of KCl

Number of moles of KCl = 4.0 mol

Mass of KCl = Moles x molar mass

= 4.0 mol x 74.5513 g / mol

= 298.205 g

q (sol) = (1000 + 298.205 ) x 4.184 x (12.3-25.0)

= -68982.50 J

Here sign is negative since temperature of the solution is decreased.

Lets calculated delta H of solution

Delta H of solution =- q solution / n

n is number of moles of solute.

Delta H solution = - ( -68982.50 J ) / 4.0 mol

= 17245.6 J / mol

Ans in kJ /mol

= 17.24 kJ /mol

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---