34. Calculate the standard enthalpy change (AH) at 298 K for the reaction of X&Y18 with O2. 2 XGY18+ 21 O2→8 XO+8 XO2 + 18 Y2O Reaction AH at 298 K 2 XaY1s+25 O,→ 16 XO, + 18 Y O -11020 kJ 2 XO +O, 2 XO, -566.0 kJ 610454 28756 kJ 1284 D11506

Using the thermodynamic tables find the enthalpy of reaction for the reaction      B2H6 (g)   +   6 F2 (g)    -->    2 BF3 (g)   +    6 HF (g)     a. – 3877 kJ b. – 3912 kJ c. + 3877 kJ d. + 3947 kJ e. – 3947 kJ f. none of these g. + 572 kJ

24. A 500-cm^3 sample of1.0 M NaOH(aq)is added to 500cm3 of 1.0M HCl(aq)in a Styrofoam cup, and the solution is quickly stirred. The rise in temperature (AT1) is measured. The experiment is repeated using 100cm^3 of each solution, and the rise in temperature (AT2) is measured. What conclusion can you draw about AT1 and AT2? HCl(aq)+NaOH(aq) H2O(1)+NaCL(aq); AH∞=-55.8KJ a. AT1 is five times as large as AT2 b. AT1 is less than AT2 c. AT2 is greater than AT1 d. AT2 is equal to AT1 e. AT2 is five times as large as AT1

Alkali metals are often used to remove traces of water from organic solvents, such as diethyl ether. Because the reaction (see below) releases heat, care must be taken to make sure that the solvent does not "boil over". 2 Na(s) + 2 H₂O(1) ➜ 2 NaOH(aq) + H₂(g) a) Determine the standard enthalpy change for this reaction. Comment on the relative strength of bonding and/or interactions in the products vs reactants, and briefly explain how you decided this. Substance Na(s) H₂O(1) NaOH(aq) H₂(g) AHºf (kJ/mol) 0 -285.83 -469.15 0 b) How much heat (in kJ) is released via the reaction of 1.00 g of sodium metal with water? If this much heat is released into 275 g of diethyl ether initially at 25°C, will the solvent reach its boiling point? If so, how many grams of the ether will evaporate? Show calculations to support your answer. For diethyl ether: Cs = 2.51 J/g⋅K, b.p. = 35°C, heat of vaporization = 377 J/g.