A chemistry graduate student is given 300. mL of a 0.80M pyridine (CHN) solution. Pyridine is a weak base with X = 1.7 × 10¯˚. What mass of CH NHCI should the student dissolve in the C₂HN solution to turn it into a buffer with pH = 5.78? You may assume that the volume of the solution doesn't change when the CH NHCI is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits. 3

Identify each pair that could form a buffer. (a) NaOH and NaCl (b) NaOH and NH3 (c) Na3PO4 and Na2HPO4

Ka for formic acid is 1.7 104 at 25C. A buffer is made by mixing 529 mL of 0.465 M formic acid, HCHO2, and 494 mL of 0.524 M sodium formate, NaCHO2. Calculate the pH of this solution at 25C after 110 mL of 0.152 M HCl has been added to this buffer.

What is the pH of a buffer that is 0.150 M in a weak acid and 0.150 M in the acids conjugate base? The acids ionization constant is 6.8 106.

You are given the following acidbase titration data, where each point on the graph represents the pH after adding a given volume of titrant (the substance being added during the titration). a What substance is being titrated, a strong acid, strong base, weak acid, or weak base? b What is the pH at the equivalence point of the tiration? c What indicator might you use to perform this titration? Explain.

A buffer is made up of 239 mL of 0.187 M potassium hydrogen tartrate (KHC4H4O6) and 137 mL of 0.288 M potassium tartrate (K2C4H4O6). Ka for is (H2C4H4O6)4.55105. Assuming volumes are additive, calculate (a) the pH of the buffer. (b) the pH of the buffer after adding 0.0250 mol of HCI to 0.376 L of the buffer. (c) the pH of the buffer after adding 0.0250 mol of KOH to 0.376 L of the buffer.

A solution is prepared by dissolving 0.350 g of benzoic acid, HC7H5O2, in water to make 100.0 mL of solution. A 30.00-mL sample of the solution is titrated with 0.272 M KOH. Calculate the pH of the solution (a) before titration. (b) halfway to the equivalence point. (c) at the equivalence point.

The titration of 0.100 M acetic acid with 0.100 M NaOH is described in the text. What is the pH of the solution when 35.0 mL of the base has been added to 100.0 mL of 0.100 M acetic acid?

Three students titrate different samples of the same solution of HCI to obtain its molarity. Below are their data. Student A: 20.00mLHCl+20.00mLH2O 0.100 M NaOH used to titrate to the equivalence point Student B: 20.00mLHCl+40.00mLH2O 0.100 M NaOH used to titrate to the equivalence point Student C: 20.00mLHCl+20.00mLH2O 0.100 M Ba(OH)2 used to titrate to the equivalence point. All the students calculated the molarities correctly. Which (if any) of the following statements are true? (a) The molarity calculated by A is half that calculated by B. (b) The molarity calculated by A is equal to that calculated by C. (c) The molarity calculated by B is twice that calculated by C. (d) The molarity calculated by A is twice that calculated by B. (e) The molarity calculated by A is equal to that calculated by B.

When a diprotic acid, H2A, is titrated with NaOH, the protons on the diprotic acid are generally removed one at a time, resulting in a pH curve that has the following generic shape: a. Notice that the plot has essentially two titration curves. If the first equivalence point occurs at 100.0 mL NaOH added, what volume of NaOH added corresponds to the second equivalence point? b. For the following volumes of NaOH added, list the major species present after the OH reacts completely. i. 0 mL NaOH added ii. between 0 and 100.0 mL NaOH added iii. 100.0 mL NaOH added iv. between 100.0 and 200.0 mL NaOH added v. 200.0 mL NaOH added vi. after 200.0 mL NaOH added c. If the pH at 50.0 mL NaOH added is 4.0, and the pH at 150.0 mL NaOH added is 8.0, determine the values Ka1, and Ka2 for the diprotic acid.