1. A 4 L sample of a diatomic gas with specific heat ratio 1.4, confined to a cylinder, is carried through a closed cycle. The gas is initially at 1 atm and 300 K. First, its pressure is tripled under constant volume. Then, it expands adiabatically to its original pressure. Finally, the gas is compressed isobarically to its original volume. Draw a P-V diagram of this cycle. Find the temperature of the gas at the start of the adiabatic expansion. Determine the volume of the gas at the end of the adiabatic expansion. Find the temperature at the end of the cycle. What is the net work done on the gas for this cycle?

2. One mole of H2 gas is contained in the left-hand side of the container, which has equal volumes left and right. The right-hand side is evacuated. When the valve is opened, gas streams into the right-hand side. What is final entropy change of the gas? Does the temperature of the gas change?

3. A 1.5 kg iron horseshoe initially at 600ºC is dropped into a bucket containing 20 kg of water at 25ºC. What is the final temperature if 100 g of water boils away? Ignore the specific heat of the container. (Specific heat of iron is 0.107 Cal/g*C. Latent heat of water vaporization is 540 cal/g)

4. Calculate the change in entropy of 250 g of water heated slowly from 20ºC to 80ºC.

Solution Summary

Answers to questions on work done on gas, entropy changes, temperature.

1) One mole of an ideal gas is changed from 273.15K and 2 atm to 233.15K and 0.4 atm. Calculate delta S for this change in state.
2) Arrange the following chemicals in order of increasing entropy at STP.
n - pentane (g)
methanol ( l)
ethanol (l)
ethanol (g)

During the quasistatic isothermal expansion of a monoatomic ideal gas, how is the change in entropy related to the heat input Q by the simple formula: ΔS = Q/T?
Why isn't this valid for the free expansion process?

Question #1
In your own words, define entropy. Provide one everyday example resulting in an increase in entropy, and another resulting in a decrease.
Question #2
About 38% of the food energy we consume is converted to chemical energy in the form of ATP, what happens to the remainder of the energy?
Question #3
When w

Using the data sheet (see attachment) calculate delta S values for the following reactions. In each case explain the sign of delta S.
N2H4(g) + H2(g) --> 2NH3(g)
2Al(s) + 3Cl2(g) --> 2AlCl3(g)
Mg[OH]2(s) + 2Hcl(g) --> MgCl2(s) + 2H20(l)
2CH4(g) --> C2H6 + H2(g)

1. Define entropy and relate to probability of microstate formation.
2. Relate entropy and reaction spontaneity, Gibbs free energy and reaction spontaneity, and Gibbs free energy and the equilibrium constant of a reaction.
3. Calculate the entropy change within a system and determine absolute entropies.
4. In your own w

One mole of an ideal gas is contained in a thermally insulated container that is connected to another container of equal volume that is initially evacuated. The valve connecting the two containers is now opened and the gas allowed to expand isothermally to fill both sides - new total volume is twice original volume.
A) What i

1) Find the standard enthalpy of cyanamide (CH3N2 (s) ) from its heat of combustion to CO2 and H2O of -741.40kJ/mol.
2) Calculate delta S if the temperature of 2.50mol of an ideal gas with Cv = 5/2R is increased from 160K to 675k under conditions of
a. constant pressure
b. constant volume

In which of the following processes will S be positive?
1. 2H2(g) + O2(g)----> 2H2O(g)
2. SO3(g) + H2O(l)-----> H2SO4(l)
3. 2KClO3(s)----->2KCl(s) + 3O2(g)
A) 2 only
B) 3 only
C) 1 and 3 only
D) 1 only
E) 1 and 2 only

Please help with the following problems.
A) Define entropy. Why is entropy considered an absolute quantity?
B) For each of the pairs of substances below, choose the one expected to have the greater absolute entropy. Explain your answer. Assume 1 mol of each substance.
i) Cu(s) or C(graphite) at the same temperatu