3. A ... in thermodynamics refers to that part of universe in which observations are made. a) Universe b) System c) Surrounding d) Boundary 4. Distinguish between endothermic and exothermic processes . If we know that a reaction is endothermic in one direction, what can be said about the reaction in the reverse direction? 5. Given: 2H_(2)(g)+O_(2)(g)arrow 2H_(2)O(c) Delta H=-571.6kJ/mol C_(3)H_(4)(g)+4O_(2)(g)arrow 3CO_(2)(g)+2H_(2)O(l) Delta H=-1937kJ/mol C_(3)H_(8)(g)+5O_(2)(g)arrow 3CO_(2)(g)+4H_(2)O(l) Delta H=-2220kJ/mol Determine the heat of the hydrogenation reaction C_(3)H_(4)(g)+2H_(2)(g)arrow C_(3)H_(8)(g) 6. Two solutions (the system), each of 25.0 mL volume and at 25.0^circ C are mixed in a beaker. A reaction occurs between them , causing the temperature to drop to 20.0^circ C After the products have equilibrated with the surroundings, the temperature is again 25.0^circ C and the total volume is 50.0 mL. No gases are involved in the reaction. Which one of the following relationships concerning the change from initial to final states (both at 25.0^circ C is correct? a. Delta E=0 b. Delta H=0 C. Delta Elt 0 d. w=0 e. q=0 7. Consider the reaction A -> products. Which of the following plots is consistent with a zero-order reaction? a. [A] plotted against time gives a horizontal straight line. b. In [A] plotted against time gives a straight line of negative slope. C. 1/[A] plotted against time gives a straight line of positive slope. d. [A] plotted against time gives a straight line of negative slope. e. [A] plotted against time gives a curved line of negative slope decreasing in magnitude as time increases.

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3. A ... in thermodynamics refers to that part of universe in which observations are made. a) Universe b) System c) Surrounding d) Boundary 4. Distinguish between endothermic and exothermic processes . If we know that a reaction is endothermic in one direction, what can be said about the reaction in the reverse direction? 5. Given: 2H_(2)(g)+O_(2)(g)arrow 2H_(2)O(c) Delta H=-571.6kJ/mol C_(3)H_(4)(g)+4O_(2)(g)arrow 3CO_(2)(g)+2H_(2)O(l) Delta H=-1937kJ/mol C_(3)H_(8)(g)+5O_(2)(g)arrow 3CO_(2)(g)+4H_(2)O(l) Delta H=-2220kJ/mol Determine the heat of the hydrogenation reaction C_(3)H_(4)(g)+2H_(2)(g)arrow C_(3)H_(8)(g) 6. Two solutions (the system), each of 25.0 mL volume and at 25.0^circ C are mixed in a beaker. A reaction occurs between them , causing the temperature to drop to 20.0^circ C After the products have equilibrated with the surroundings, the temperature is again 25.0^circ C and the total volume is 50.0 mL. No gases are involved in the reaction. Which one of the following relationships concerning the change from initial to final states (both at 25.0^circ C is correct? a. Delta E=0 b. Delta H=0 C. Delta Elt 0 d. w=0 e. q=0 7. Consider the reaction A -> products. Which of the following plots is consistent with a zero-order reaction? a. [A] plotted against time gives a horizontal straight line. b. In [A] plotted against time gives a straight line of negative slope. C. 1/[A] plotted against time gives a straight line of positive slope. d. [A] plotted against time gives a straight line of negative slope. e. [A] plotted against time gives a curved line of negative slope decreasing in magnitude as time increases.

Answer 1

3. b) System 4. Endothermic processes absorb heat from the surroundings, while exothermic processes release heat to the surroundings. If a reaction is endothermic in one direction, it will be exothermic in the reverse direction. 5. To determine the heat of the hydrogenation reaction, we can use Hess's Law. By manipulating the given reactions, we can obtain the desired reaction: $C_{3}H_{4}(g) + 2H_{2}(g) \rightarrow C_{3}H_{8}(g)$ Using the given reactions, we can write: $C_{3}H_{4}(g) + 4O_{2}(g) \rightarrow 3CO_{2}(g) + 2H_{2}O(l)$ $\Delta H = -1937 kJ/mol$ $C_{3}H_{8}(g) + 5O_{2}(g) \rightarrow 3CO_{2}(g) + 4H_{2}O(l)$ $\Delta H = -2220 kJ/mol$ By reversing the first reaction and adding it to the second reaction, we get the desired reaction: $C_{3}H_{4}(g) + 2H_{2}(g) \rightarrow C_{3}H_{8}(g)$ The heat of the reaction is the difference between the heats of the two reactions: $\Delta H = -1937 kJ/mol - (-2220 kJ/mol) = 283 kJ/mol$ Therefore, the heat of the hydrogenation reaction is 283 kJ/mol. 6. a. $\Delta E=0$ 7. a. $[A]$ plotted against time gives a horizontal, straight line.

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