Question

Calculate the standard enthalpy change (∆H°) for the dissolution reaction of 5.00 grams of sodium chloride (NaCl) in 100.0 mL of water, given that the final temperature of the solution was 25.0°C and the heat capacity of the solution was 4.18 J/g°C. The molar mass of NaCl is 58.44 g/mol and the density of water is 1.00 g/mL.

Answer 1

To calculate the standard enthalpy change  H  for the dissolution reaction of sodium chloride  NaCl  in water, we first need to determine the amount of heat  q  absorbed or released during the process. We can use the formula:q = mcTwhere m is the mass of the solution, c is the heat capacity of the solution, and T is the change in temperature.First, let's find the mass of the solution. Since the density of water is 1.00 g/mL, the mass of 100.0 mL of water is 100.0 g. Adding the mass of NaCl  5.00 g , we get:m_solution = 100.0 g  water  + 5.00 g  NaCl  = 105.0 gNext, we need to determine the change in temperature  T . Since the final temperature of the solution is 25.0C, we can assume that the initial temperature of both water and NaCl was also 25.0C  as they are mixed at the same temperature . Therefore, there is no temperature change in this case:T = 0CNow, we can calculate the heat  q  using the formula:q = mcT =  105.0 g  4.18 J/gC  0C  = 0 JSince there is no heat absorbed or released during the dissolution process, the standard enthalpy change  H  for the dissolution reaction of sodium chloride in water is also 0 J.