Physical Chemistry Answers

1. A solution of NaCl is neutral, with an expected PH of 7. If electrolysis was carried out on 500 mL of an NaCl solution with a current of 0.500 A, how many seconds would it take for the PH of the solution to rise to a value of 9? (PH is related to H+ concentration by PH = -log [H+]).

One component of an ideal binary solution has a pure component vapor pressure equal to one-fourth the total pressure of the vapor mixture. The component constitutes 20 mole % of liquid phase. What is its mole fraction in the vapor phase?

There is a certain chemical reaction that involves two reactants producing one product. A perfect chemist performs this reaction using 50.0 grams of each reactant, and produced 82.0 grams of product.
What is the amount, in grams, of the excess reactant?

How much concentration of HCL is needed in the preparation of 500 mL of solution HCL

Three 1.0 liter flasks are filled with H2, O2, and Ne, respectively, at STP.

Which of the following statements is true?

Each flask has the same number of gas molecules.
The density of each gas is the same
There are twice as many oxygen and hydrogen molecules as neon atoms
None of the options are true

(a) CFor the following reaction at equilibrium at 2000°C, the concentration of N 2 and O are both
5.2 M.

N 2 (g) + O 2 (g) ↔ 2 NO 2 (g) K eq = 6.2 × 10 -4

Calculate the concentration of NO at equilibrium.
(b) Acetic acid, HC 2 H 3 O 2 , is in equilibrium with its ions:

HC 2 H 3 O 2 (aq) ↔ H + (aq) + C 2 H 3 O 2 – (aq) K eq = 1.8 × 10 -5

At equilibrium, the concentration of the ions are:
[H + ] = 1.33 × 10 -3 M
[C 2 H 3 O 2 – ] = 1.33 × 10 -3 M
Calculate the concentration of the acid, HC 2 H 3 O

(a) Calculate the pH of a solution resulting from adding 4 mL of 0.2 M of NaOH solution to
16 mL of a buffer solution containing 0.1 M CH3COOH ( Ka = 1.8X10-5 ) and 0.2 M
CH3COONa ?
(b) Calculate the pH of a solution resulting from adding 6 mL of 0.2 M HCl to 14 mL of a buffer
solution containing 0.2 M NH3 ( Kb = 1.75X10-5 ) and 0.1 M NH4Cl

A 0.789g sample of impure magnesium oxide was dissolved in 25 cm3 of 1 mol dm-3 Sulfuric acid. The resulting solution was made up to 100cm3 with water. 25 cm3 of this final solution were neutralized by 27.8 cm3 of 0.1 mol dm-3 sodium hydroxide. Calculate the percentage purity of the magnesium oxide.

5 Which molecules of simple hydrocarbons may interfere after ionization with
the masses of oxygen 16O, 17O and 18O when measured with a mass
spectrometer? How can we make sure they are absent