Question

A calorimeter contains 30.0 mL of water at 15.0 °C. When 1.30 g of X (a substance with a molar mass of 44.0 g/mol ) is added, it dissolves via the reaction X(s) + H2O(1) X(aq) and the temperature of the solution increases to 26.5 °C. Calculate the enthalpy change, AH, for this reaction per mole of X. Assume that the specific heat of the resulting solution is equal to that of water [4.18J/(g. °C)], that density of water is 1.00 g/mL, and that no heat is lost to the calorimeter itself, nor to the surroundings. Express the change in enthalpy in kilojoules per mole to three significant figures.

Answer 1

To calculate the change in enthalpy, use the equation q = mcΔT, where q is the heat absorbed or released, m is the mass of the solution, c is the specific heat of the solution, and ΔT is the change in temperature.

Step-by-step explanation:

In this question, we are given the initial and final temperatures of a solution when a substance is added to it. We are also told the specific heat and density of water. We need to calculate the change in enthalpy for the reaction per mole of the substance added.

To calculate the change in enthalpy (ΔH), we can use the equation q = mcΔT, where q is the heat absorbed or released, m is the mass of the solution, c is the specific heat of the solution (which is the same as that of water), and ΔT is the change in temperature. We can calculate the mass of the solution by adding the mass of the water to the mass of the substance added. From the molar mass of the substance and the given mass, we can calculate the number of moles of the substance added. Finally, we can divide the heat change by the number of moles to get the change in enthalpy per mole of the substance.