12. Calculate pH in a 0,05M solution of Na2HPO4 (a buffer in water Ka3 for phosphoric acid)

You add 0.979 g of Pb(OH)2 to 1.00 L of pure water at 25 C. The pH is 9.15. Estimate the value of Ksp for Pb(OH)2.

What will be the pH of a buffer solution prepared from 0.20 mol NH3, 0.40 mol NH4NO3, and just enough water to give 1.00 L of solution?

A buffer is prepared by dissolving 0.0250 mol of sodium nitrite, NaNO2, in 250.0 mL of 0.0410 M nitrous acid, HNO2. Assume no volume change after HNO2 is dissolved. Calculate the pH of this buffer.

Weak base B has a pKb of 6.78 and weak acid HA has a pKa of 5.12. a Which is the stronger base, B or A? b Which is the stronger acid, HA or BH+? c Consider the following reaction: B(aq)+HA(aq)BH+(aq)+A(aq) Based on the information about the acid/base strengths for the species in this reaction, is this reaction favored to proceed more to the right or more to the left? Why? d An aqueous solution is made in which the concentration of weak base B is one half the concentration of its acidic salt, BHCl, where BH+ is the conjugate weak add of B. Calculate the pH of the solution. e An aqueous solution is made in which the concentration of weak acid HA twice the concentration of the sodium salt of the weak acid, NaA. Calculate the pH of the solution. f Assume the conjugate pairs B/BH+ and HA/A are capable of being used as color-based end point indicators in acidbase titrations, where B is the base form indicator and BH is the acid form indicator, and HA is the acid form indicator and A is the base form indicator. Select the indicator pair that would be best to use in each of the following titrations: (1) Titration of a strong acid with a strong base. (i) B/BH+ (ii) HA/A (2) Titration of a weak base with a strong acid. (i) B/BH+ (ii) HA/A

A friend asks the following: Consider a buffered solution made up of the weak acid HA and its salt NaA. If a strong base like NaOH is added, the HA reacts with the OH to form A. Thus the amount of acid (HA) is decreased, and the amount of base (A) is increased. Analogously, adding HCI to the buffered solution forms more of the acid (HA) by reacting with the base (A). Thus how can we claim that a buffered solution resists changes in the pH of the solution? How would you explain buffering to this friend?

What volume of 0.120 M NaOH must be added to 100. mL of 0.100 M NaHC2O4 to reach a pH of 4.70?

A solution is made by diluting 25.0 mL of concentrated HCl (37% by weight; density = 1.19 g/mL) to exactly 500 mL. Calculate the pH of the resulting solution.

A bottle of concentrated hydroiodic acid is 57% HI by weight and has a density of 1.70 g/mL. A solution of this strong and corrosive acid is made by adding exactly 10.0 mL to some water and diluting to 250.0 mL. If the information on the label is correct, what volume of 0.988 M NaOH is needed to neutralize the HI solution? Suggest an indicator for the titration.

Follow the directions of Question 64. Consider two beakers: Beaker A has a weak acid(K a=1105). Beaker B has HCI. The volume and molarity of each acid in the beakers are the same. Both acids are to be titrated with a 0.1 M solution of NaOH. (a) Before titration starts (at zero time), the pH of the solution in Beaker A is the pH of the solution in Beaker B. (b) At half-neutralization (halfway to the equivalence point), the pH of the solution in Beaker A the pH of the solution in Beaker B. (c) When each solution has reached its equivalence point, the pH of the solution in Beaker A the pH of the solution in Beaker B. (d) At the equivalence point, the volume of NaOH used to titrate HCI in Beaker B the volume of NaOH used to titrate the weak acid in Beaker A.