I. (18 pts) The thermochemical equation for the dissolution of calcium chloride

Question

I. (18 pts) The thermochemical equation for the dissolution of calcium chloride is CaCl2(s) ?Ca2+(aq) + 2 Cl"(aq) Mf=-81,5 kJ/mol A. Circle the correct answer (3 pts) oissolving Cacials] in wateris ov sxolhermcdothemic process. 3 Energy is transferred as heat from the stern/suroundings to the systenstauroundings # 15.0 g CaCi2 is odded to 125 g H20 at 23.6 C in a coffee cup calorimeter. Assume the specific heat of the solution is 4.18 J/g°C. (Molar masses: CaCi2: 110.98 g/mol; H2O: 18.02 g/mol) B, Calculate Gr. (6pts) gryn nDHrvn 110, 5.02 7C4)C-236) D. What is the final temperature of the solution? (5pts) ?1403° 4.16 (F-23.6%) 23.b 3

Explanation / Answer

8. for the dissolution of CaCl2

A.

a. it is an exothermic reaction

b. energy from system transferred to surrounding

B. calorimetric experiment

moles CaCl2 = 15 g/110.98 g/mol = 0.135 mols

qrxn = -81.5 kJ/mol x 0.135 mol = -11.0 kJ

C. qsolution = 11.0 kJ = 11000 J

D. let Tf be final temperature

11000 = (15+125) x 4.184 x (Tf - 23.6)

Tf = 42.4 oC

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