Suppose you have a calorimeter that contains 100.0 grams of water at an initial temperature of 25*c. a salt (2.19 g, 0.020 moles) is dissolved in the water, and the final temperature is 29*c. calculate the standard heat of solution (on a per mole basis). was the dissolution exothermic or endothermic?

The standard heat of the solution is 85512.5 J/mol and the reaction is endothermic in nature.

Explanation:

To calculate the heat released or absorbed, we use the equation:

where,

q = heat absorbed or released

m = mass of solution = (100 + 2.19) g = 102.19 g

c = specific heat capacity of water = 4.184 J/g.°C

= change in temperature =

Putting values in above equation, we get:

Sign convention of heat:

When heat is absorbed, the sign of heat is taken to be positive and when heat is released, the sign of heat is taken to be negative.

To calculate the enthalpy change of the reaction, we use the equation:

where,

= amount of heat absorbed = 1710.25 J

n = number of moles = 0.020 moles

= standard enthalpy change of the reaction

Putting values in above equation, we get:

Hence, the standard heat of the solution is 85512.5 J/mol and the reaction is endothermic in nature.

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