Pre-Lab Exercise ppose you have a calorimeter that contains 100.0 grams of water

Question

Pre-Lab Exercise ppose you have a calorimeter that contains 100.0 grams of water at an initial temperaru of 25 °C. A salt (2.19 g, 0.020 moles) is d 29 oC. Calculate the standard heat of solution (on a per mole basis). Was the dissolution issolved in the water, and the final temperature is exothermic or endothermic? The P r is defined as "the enthalpy change for the formation of one mole of a substance from its elements in their standard states." For example, the heat of formation, AHP of CO, is C(graphite) + O2(g) CO2(g) Note that we use carbon in the form of graphite since this is the standard state for carbon, and diatomic oxygen, since this is the standard state for oxygen. Write the chemical reaction that correlates to the Hof of KCI 2.

Explanation / Answer

Q1.

Qwater = m*C*(Tf-Ti)

Qwater = 100*4.184*(29-25)

Qwater = 1673.6 J

mol = 0.02

HRxn = -Qwater/mol = -1673.6 / 0.02 = - 83680

HRxn = -83.680 kJ/mol

Q2.

KCl(s) is formed by:

K and CL ions

then

K = K(s) is elemental, Cl = Cl2(g) elemental

the reaction

K(s) + Cl2(g) --> KCl(s)

balance

K(s) + 1/2Cl2(g) --> KCl(s)

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