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Sch2106:Physical Chemistry Question Paper
Sch2106:Physical Chemistry
Course:Bachelor Of Horticulture
Institution: Meru University Of Science And Technology question papers
Exam Year:2011
QUESTION ONE (20 MARKS)
a. Explain withes examples the difference between a state function and a path function (4 Marks) b. Energy can take on a variety of forms. Give examples. (3 Marks) c. Sodium azide (NaN3) is used in some automibile as bags. The impact of a collision triggers the decomposition of NaN3 as follows. 2 NaN3 (s) ?2 NaN3 (g) The Nitrogen gas produced quickly inflates the bag between the driver and the bond. Calculate the volume of N2 generated at 80°c and 1.083 atm by the decomposition of 60.0 g of NaN3. R = 0.0321 L atm k-1mol-1. (5 Marks) d. Which of the following condition cause deviation from ideal gas behavior? Select all that apply. (2 Marks) i. High pressure ii. Low pressure iii. High temperature iv. Low temperature v. High volume e. Calculate the charge in total internal energy for a system that releases 1.34x104kj of heat and does 2.98x104kj of work on the surroundings. (3 Marks) f. Explain the difference between contract volume heat capacity and constant pressure heat capacity. (4 Marks) g. Write the equation for calculating Gibbs free energy (DG) and explain the terms (3 Marks)
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h. Explain a dynamic equilibrium (2 Marks)
i. Explain how buffers work through the phenomenon knows as the common effect (4 Marks)
QUESTION TWO (20 MARKS)
a. The gas laws help us to predict the behavior of gases, but they do not explain what happens at the molecular level to cause the changes we observe in the macroscopic world. Boltzmann and Maxwell found that the physical properties of gases can be explained in terms of the motion of individual molecules. State the generalization about gas behavior known as kinetic molecular theory of gases (8 Marks) b. In a reversible expansion under infinitesimal changes, we set external pressure of a gas equal to internal pressure for the gas. In an isothermal reversible expansion, derive the expression for expansion work. (6 Marks) c. Given the thermo chemical equation SO2 (g) + 1 2 O2 (g) ?SO3 (g) DH =-99.1 kj/mol. Calculate the heat involved when 74.6 of SO2IS converted to SO3 molar mass of SO2=64.07g/mol (6 Marks)
QUESTION THREE (20 MARKS)
a. What is q, w, DE and DH for a process in which are mole of an ideal of monatomic gas with an initial volume of 5L and pressured of 2.0 atm is heated until a volume of 10L is reached with pressured unchanged? (10 Marks) b. Explain the conditions when entropy (DS) becomes zero (o) (2 Marks) c. Predict whether each of the following leads to an increase or decrease in the entropy of a system (5 Marks) d. The thermite reaction involves aluminium and iron 111 oxide 2 AL (s) + Fe2O3 (s) ?AL2O3 (s) + 2 Fe (?) IS 12.40KJ/MOL, DHf°(AL2O3) = - 1669.8 KJ/mol and DHf°(Fe2O3) = -822.2kj/mol(3 Marks)
QUESTION FOUR (20 MARKS)
a. What is the standard free energy change (Drxn) for the following reaction, and what is the free energy change for the mixture of gasses at 25° c if all of the gases i.e. N2, H2 and NH3 ARE AT 0.10 atm. N2 (g) + 3H2 (g) ??2NH3 (g)
Take ???°f (NH3) = -16.66kj/mol, ?G°f (N2) =0, ?G°f (H2) = 0
b. What is the PH of buffer solution consisting of 0.50 m CH3COOH (HAC) and 0.50 m CH3COONa (Na,Ac) after adding 0.20 mol of solid NaOH to 1L of the solution Ka(CH3C00H ) = 1.8X105. (7 Marks) c. The Henderson-Hasselbach equation is a follows PH = pKa + Log (???????? ???????? )
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