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03 Enthalpy

# 03 Enthalpy - Problem of the Day(from Wed H2 reacts with O2...

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1 Problem of the Day (from Wed) H 2 reacts with O 2 producing H 2 O in a fuel cell to power an electric motor in a car. The motor produces 75 kW of power (1 watt = 1J/s) to move the car and runs for 2 min 20 s. During this period, 5.0 x 10 3 kJ of heat is produced. What is the change in the internal energy of the reacting system 2H 2 + O 2 H 2 O in the fuel cell? E system = q + w 2 H 2 reacts with O 2 producing H 2 O in a fuel cell to power an electric motor in a car. The motor produces 75 kW of power (1 watt = 1J/s) to move the car and runs for 2 min 20 s. During this period, 5.0 x 10 3 kJ of heat is produced. What is the change in the internal energy of the reacting system 2H 2 + O 2 H 2 O in the fuel cell? A. - 10,500 kJ B. - 5,000 kJ C. - 15,500 kJ D. + 15,500 kJ E. + 10,500 kJ

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3 Use An Expert Problem Solving Process The eze way Visualize Organize Analyze Exercise Legitimize VCOAST* Visualize Collect & Organize Analyze Solve It Think About It *Tom Gilbert, Northeastern University, Boston 4 2H 2 + O 2 2H 2 O Fuel Cell System Visualize & Organize Analyze The big idea is conservation of energy: E system = q + w Energy is transferred to the surroundings. Work is done on the surroundings. So the energy of the system must go down. E system = E final - E initial E final < E initial so E system < 0 (i.e. is negative) Both q and w are negative representing that energy is transferred to the surroundings and work is done on the surroundings.
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03 Enthalpy - Problem of the Day(from Wed H2 reacts with O2...

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