Thermodynamics

Consider the formation reactions below and pick the most stable species from the answer choices.

2C_graphite(s) + 3H₂(g) → C₂H₆(g) 

∆G◦ _f = −7.86 kcal · mol⁻¹

3Cgraphite(s) + 4H₂(g) → C₃H₈(g)

∆G◦ f = −5.614 kcal · mol⁻¹

8Cgraphite(s) + 9H₂(g) → C₈H₁₈(g)

∆G◦ _f = 4.14 kcal · mol⁻¹

10Cgraphite(s) + 11H₂(g) → C₁₀H₂₂(g)

∆G◦ _f = 8.23 kcal · mol⁻¹

1. The change in entropy is large. 

2. The change in entropy is small. 

3. The reaction is endothermic. 

4. The reaction is exothermic

Consider the equation NH₄Br(s) → NH₃(g) + HBr(g) carefully, and think about the sign of ∆S for the reaction it describes. ∆H = +188.3 kJ. Which response describes the thermodynamic spontaneity of the reaction? 

1. The reaction is spontaneous only at relatively low temperatures. 

2. All responses are 

3. The reaction is spontaneous at all temperatures. 

4. The reaction is not spontaneous at any temperatures. 

5. The reaction is spontaneous only at relatively high temperatures

Helium gas expands from 125 kPa, 350 K and 0.25 m3 to 100 kPa in a polytropic process with n = 1.667. Is the work positive, negative or zero?

A manometer shows a pressure difference of 1 m of liquid mercury. Find ∆P in kPa.

A polytropic flow process with n = 0 might be which device? 

 The pressure of a gas in a pipeline is measured with a mercury manometer having one limb open. The difference in the level of the two limbs is 562mm. Calculate the gas pressure in terms of bar.

How can you change s of a substance going through a reversible process?

Determine the mass of an ethane gas stored in a 25 ft³ tank at 250 F, 440 lbf/in.² using the compressibility chart. Estimate the error (%) if the ideal gas model is used. 

In a cylinder–piston arrangement, 2kg of an ideal gas are expanded adiabatically from a temperature of 125°C to 30°C and it is found to perform 152KJ of work during the process while its enthalpy change is 212.8KJ. Find its specific heats at constant volume and constant pressure and characteristic gas constant.

Define different types of properties?