Question

0.9775 grams of an unknown compound is dissolved in 50.0 ml of water. Initially the water temperature is 22.3 degrees Celsius. After addition of the solid, the solution temperature is raised to about 27.0 degrees Celsius. The substance is known to have a molar mass of about 56 g/mol. Calculate the enthlapy of solution in kJ/mol.

Answer 1

To calculate the enthalpy of solution, use the formula ΔH = q / n, where ΔH is the enthalpy change, q is the heat transferred, and n is the number of moles dissolved. Plug in the values for mass, specific heat, and change in temperature to find the heat transferred. Divide the mass of the compound by the molar mass to find the number of moles dissolved. Finally, calculate the enthalpy of solution by dividing the heat transferred by the number of moles dissolved.

Step-by-step explanation:

To calculate the enthalpy of solution, we need to use the formula: ΔH = q / n, where ΔH is the enthalpy change, q is the heat transferred, and n is the number of moles dissolved. First, we need to find the heat transferred. We can use the formula q = mc∆T, where q is the heat transferred, m is the mass of the water, c is the specific heat of water, and ∆T is the change in temperature. ∆T = Tfinal - Tinitial = 27.0°C - 22.3°C = 4.7°C. Plugging in the values, q = (50.0 g)(4.184 J/g°C)(4.7°C) = 987.04 J.

To find the number of moles dissolved, we divide the mass of the compound by the molar mass. n = 0.9775 g / 56 g/mol = 0.01745 mol. Now we can calculate the enthalpy of solution: ΔH = q / n = 987.04 J / 0.01745 mol = 56528.6 J/mol. Converting to kilojoules, ΔH = 56.5286 kJ/mol.