1. Explain what a state function is and give an example. 2. Define enthalpy. 3.

Question

1. Explain what a state function is and give an example.

2. Define enthalpy.

3. Does the enthalpy change in burning a fuel depend on whether it is a solid, liquid, or gas?

4. Given the following reactions determine the standard enthalpy of formation of methane (CH4) from graphite [C(graphite)+2H2(g)-->CH4(g)]:

a. C(graphite)+O2(g)-->CO2(g)    delta H reaction= -393.5 kJ

b. 2H2(g)+O2(g)-->2H2O(I)    delta H reaction= -571.6 kJ

c. CH4(g)+2O2(g)-->CO2(g)+2H2O(I) delta H reaction= -890.4 kJ

5. Explain why you were able to solve problem 4 as you did.

Explanation / Answer

1) A state function is a thermodynamic quantity,,that is the characteristic of its state,it has a unique value for every different state of a system.

Example :enthalpy or heat changes for a system is a state function ,

For two states of the system S1   and S2, the enthalpy value of a system will be same for both irrespective of either path A is chosen to reach from S1 to S2 or path B is chosen for the change.

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