Question

Calculate the enthalpy change of solution for 5.00 g of ammonium chloride (NH4Cl) dissolved in 50.0 mL of water, given that the temperature of the solution decreases by 4.21°C. The density of water is 1.00 g/mL and the specific heat capacity of the solution is 4.18 J/g°C. The molar mass of ammonium chloride is 53.49 g/mol.

Answer 1

To calculate the enthalpy change of solution, we first need to find the heat absorbed or released by the solution  q . We can do this using the formula:q = mass  specific heat capacity  change in temperatureThe mass of the solution is the sum of the mass of ammonium chloride and the mass of water. Since the density of water is 1.00 g/mL, the mass of 50.0 mL of water is 50.0 g. Therefore, the mass of the solution is:mass_solution = mass_NH4Cl + mass_water = 5.00 g + 50.0 g = 55.0 gThe change in temperature is given as -4.21C  since the temperature decreases . Now we can calculate the heat absorbed or released by the solution:q =  55.0 g    4.18 J/gC    -4.21C  = -966.729 JSince the temperature of the solution decreases, the heat is released, and the enthalpy change  H  is positive. Therefore, H = +966.729 J.Now we need to find the moles of ammonium chloride  NH4Cl  dissolved:moles_NH4Cl = mass_NH4Cl / molar_mass_NH4Cl = 5.00 g / 53.49 g/mol = 0.0935 molFinally, we can calculate the enthalpy change of solution per mole of NH4Cl:H_solution = H / moles_NH4Cl = 966.729 J / 0.0935 mol = 10334.5 J/molThe enthalpy change of solution for ammonium chloride is approximately 10.3 kJ/mol.