CaCl2(s) Ca2 (aq)+2C1 (aq) When 3.195 g of calcium chloride is added to 50.00 mL

Question

CaCl2(s) Ca2 (aq)+2C1 (aq) When 3.195 g of calcium chloride is added to 50.00 mL of water inside a coffee-cup calorimeter, the temperature of the water changes from 25.0°C to 36.2°C. The density of the solution is 1.00 g/mL and the specific heat of the solution is 4.18 J/g. C. a. Calculate ??1rxn (in kJ/mol) for the dissolution of calcium. chloride. b. How much heat is absorbed/released when 6.123 g of calcium chloride dissolves? c. Using the given ??? values and the ?????, calculate ??? of chloride ions (CI). Compound | AH (kJ/mol) CaCl2 Ca2+ -795.4 542.8

Explanation / Answer

(a)

q = mass * specific heat * change in temperature

q = 50.00 * 4.184 * ( 36.2 - 25.0 )

q = 2343.04 J

Mass of CaCl2 = 3.195 g.

Molar mass of CaCl2 = 111. g/mol

Moles of CaCl2 = 3.195 / 111.= 0.0288 mol

deltaH = - q / n = - 2343.04 / 0.0288 = - 81401 J / mol = - 81.4 kJ / mol

(b)

Heat released when 6.123 g. of CaCl2 is dissolved = - 81.4 * 6.123 / 111. = 4.49 kJ

(c)

deltaH0r = deltaH0f(Ca2+) + 2 * deltaH0f(Cl-) - deltaH0f(CaCl2)

- 81.4 = - 542.8 + 2 * deltaH0f(Cl-) - ( - 795.4 )

deltaH0f(Cl-) = - 167 kJ/mol

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