Physical Chemistry Answers

A buffer solution is prepared by dissolving 1.50 g each of benzoic acid, C7H6O2, and

sodium benzoate, NaC7H5O2, in 150.0 mL of solution. [Ka = 6.3 x 10-5]

a. What is the pH of this buffer solution?

b. Which buffer component must be added, and in what quantity, to change the

buffer pH to 4.00?

c. What quantity of 2.0 M NaOH or 2.0 M HCl must be added to the original buffer to

change the pH to 4.00.

You have two test tubes T1 and T2 . T1 contains 2.0 mL of 0.1 N CuCl2 solution and T2 contains 2.0 mL of 0.1 N NiCl2 solution. You add dil. HCl in both the test tubes till the solutions turns acidic. Then you pass H2S gas in both the test tubes. In which of the two test tubes precipitation will occur readily? What is the principle behind the formation of precipitate?

Find the weight of H, stored in 100-cm' cylindrical tank at 100 °C and 100 atm (10, 132.5 KPa) using (a) Ideal gas equation (b) van der Waals equation if a = 0.244 atm-L²/mole and b = 0.0266 L/mole. (Note: Use the method of successive approximation to solve for the mass of H₂)

Can a solution be saturated but dilute? If yes give example?

Give 2 examples of a process in which the Entropy of the system decreases but the entropy of the Universe increases.

Derive Gibb’s-Helmholtz Equation.

What should be the ratio of concentrations of acetic acid and acetate ions to have a solution with pH 5.74? [pKa for acetic acid is 4.74].

Draw the Pressure v/s Volume graph for all the 4 steps of the Carnot Cycle and state which steps are isenthalpic (Involve no change entropy). Can a Carnot engine be 100 % efficient?

The system Carbonic acid and sodium hydrogen carbonate is found in blood and helps in maintaining the pH of blood close to 7.4.

Case I- Any excess of H+ entering blood is removed by HCO3- ion, Case II - Any excess of OH- entering blood is removed by H2CO3. Write the reactions for the above two cases.

You have two test tubes T1 and T2.

T1 contains 2.0 mL of 0.1 N CuCl2 solution and T2 contains 2.0 mL of 0.1 N NiCl2 solution. You add dil. HCl in both the test tubes till the solutions turns acidic. Then you pass H2S gas in both the test tubes. In which of the two test tubes precipitation will occur readily? What is the principle behind the formation of precipitate?