CHE 111 - OQ 8 Thermodynamics

CHE 111 - OQ 8 Thermodynamics Complete the sentence: When heat is transferred to the system, the process is said to be ____________, and the sign of q is __________. 1. exothermic, positive 2. exothermic, negative 3. endothermic, positive 4. endothermic, negative 5. forbidden, indeterminate - Answer- 3. endothermic, positive What is the equation for the formation reaction for gaseous hydrazine, N2 H4, at 25ºC and 1 atm pressure? 1. N2 + H4 (g) → 2NH3 (g) + H2 (g) 2. 2 NH3 (g) + H2 (g) → N2 H4 (g) 3. N2 (g) + 2H2 O(g) → N2 H4 (g) + O2 (g) 4. N2 (g) +2H2 (g) → N2 H4 (g) 5. 2NO2 (g) + 6H2 (g) → N2 H4 (g) + 4H2 O(g) - Answer- 4. N2 (g) +2H2 (g) → N2 H4 (g) The dissolution of barium hydroxide in water is an exothermic process. Which statement is correct? 1. The enthalpy of solid barium hydroxide plus pure water is less than that of the solution, at the same temperature. 2. The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature. 3. The enthalpy of solid barium hydroxide plus pure water is the same as that of the solution, at the same temperature. 4. The temperature of the solution is lower than of the barium hydroxide and water before mixing. 5. When barium hydroxide dissolves in water, the system does work on the surroundings. - Answer- 2. The enthalpy of solid barium hydroxide plus pure water is greater than that of the solution, at the same temperature. What is q if 28.6 g of water is heated from 22.0°C to 78.3°C? The specific heat of water is 4.184 J/g·°C. 1) 2.60 J 2) 2.63 kJ 3) 6.74 kJ 4) 9.37 kJ 5) 3.94×104kJ - Answer- 3) 6.74 kJ Ethylene glycol, used as a coolant in automotive engines, has a specific heat capacity of 2.42 J/g·°C. Calculate q when 3.65 kg of ethylene glycol is cooled from 132°C to 85°C. 1. -1900 kJ 2. -420 kJ 3. -99 kJ 4. -0.42 kJ 5. -4.2 × 10-6 kJ - Answer- 2. -420 kJ