Question

Calculate the enthalpy change of dissolution (in kJ/mol) for NaCl in water, given that 1.00 g of NaCl is dissolved in 50.0 mL of water at 25°C. The density of water is 0.997 g/mL and the specific heat capacity of the solution is assumed to be the same as that of water (4.184 J/gK). The molar mass of NaCl is 58.44 g/mol.

Answer 1

To calculate the enthalpy change of dissolution, we need to first find the heat absorbed or released by the solution when NaCl dissolves. We can do this using the formula:q = mcTwhere q is the heat absorbed or released, m is the mass of the solution, c is the specific heat capacity, and T is the change in temperature.Since the specific heat capacity of the solution is assumed to be the same as that of water, we can use the given value of 4.184 J/gK. We also know that the mass of NaCl is 1.00 g, and the volume of water is 50.0 mL. We can find the mass of water using the given density:mass of water = volume  density = 50.0 mL  0.997 g/mL = 49.85 gNow we can find the total mass of the solution:mass of solution = mass of NaCl + mass of water = 1.00 g + 49.85 g = 50.85 gSince the problem does not provide the change in temperature  T , we will assume that the temperature remains constant at 25C. This means that the heat absorbed or released by the solution  q  is zero.Now we can calculate the moles of NaCl dissolved:moles of NaCl = mass of NaCl / molar mass of NaCl = 1.00 g / 58.44 g/mol = 0.0171 molFinally, we can find the enthalpy change of dissolution  H  using the formula:H = q / moles of NaCl = 0 J / 0.0171 mol = 0 kJ/molSince the heat absorbed or released by the solution is zero, the enthalpy change of dissolution for NaCl in water at 25C is 0 kJ/mol.