Week 10 Question 2

When doing a titration of a polyprotic acid, one starts with a solution of the polyprotic acid in a flask and incrementally adds titrant (strong base such as NaOH) to the solution. The pH can be calculated at various points in the titration, starting with zero added titrant. Some very useful points are the half-equivalence point, the first equivalence point, half way to the second equivalence point and the second equivalence point. 

Using the system of 25.0 mL of 0.050 M malonic acid, H₂C₃H₂O₄ titrated with 0.025 M NaOH, calculate the pH at the following points: 

    First person: zero added NaOH (initial point in the titration)

    Second person: first half equivalence point

    Third person:   first equivalence point

    Fourth person: second half equivalence point

    Fifth person:  second equivalence point

    Sixth person: after adding 150 mL of the NaOH

If we finish with this, I will put up a second system.

Week 10 Question 1

Determine the pK_x (meaning either pK_a or pK_b based upon whether it is an acid or a base) of the following species in solution, then choose another compound for the next person to determine the pK_xvalue.

(CH₃)₃NH⁺

Week 9 Question 2

Identify the following as an acidic, basic or neutral salt: CH₃NH₃Cl.

Choose another salt for the next person to answer.

Week 9 Question 1

What is the pH of a 0.10 M aqueous solution of CH₃NH₂? The Kb is 4.4x10⁻⁴.

Choose another acid, base or salt for the next person to answer.

Week 8

Identify the following compound as a weak acid, weak base, strong acid, strong base, acidic salt, basic salt or neutral salt and finally identify what species would be present in aqueous solution: HCNO

Choose another compound for the next person.