A chemistry graduate student is given 100. mL of a 0.40M nitrous acid (HNO,) solution. Nitrous acid is a weak acid with K=4.5 x 10 What mass of NaNO, should the student dissolve in the HNO, solution to turn it into a buffer with pH = 3.16? You may assume that the volume of the solution doesn't change when the NaNO, is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits.

A buffer solution is prepared by adding 5.50 g of ammonium chloride and 0.0188 mol of ammonia to enough water to make 155 mL of solution. (a) What is the pH of the buffer? (b) If enough water is added to double the volume, what is the pH of the solution?

Sketch the titration curve for a weak acid titrated by a strong base. When performing calculations concerning weak acidstrong base titrations, the general two-slep procedure is to solve a stoichiometry problem first, then to solve an equilibrium problem to determine the pH. What reaction takes place in the stoichiometry part of the problem? What is assumed about this reaction? At the various points in your titration curve, list the major species present after the strong base (NaOH, for example) reacts to completion with the weak acid, HA. What equilibrium problem would you solve at the various points in your titration curve to calculate the pH? Why is pH 7.0 at the equivalence point of a weak acid-strong base titration? Does the pH at the halfway point to equivalence have to be less than 7.0? What does the pH at the halfway point equal? Compare and contrast the titration curves for a strong acidstrong base titration and a weak acidstrong base titration.

A 1.0-L solution that is 4.2 M in ammonia is mixed with 26.7 g of ammonium chloride. a What is the hydroxide-ion concentration of this solution? b 0.075 mol of MgCl2 is added to the above solution. Assume that there is no volume change. After Mg(OH)2 has precipitated, what is the molar concentration of magnesium ion? What percent of the Mg2+ is removed from solution?