Question

In the Acid-Base Chemistry Experiment the measurement of pH will be used to explore acid-base concepts, analyze an unknown, and determine percent K and Fe in the iron salt. The pH is measured using pH paper, acid-base indicators, and a combination pH electrode. Quantitative measurements are made using a combination pH electrode interfaced with a computer in a pH titration using dilute NaOH. The molarity of a strong acid (HCl), equivalent weight and pKa of an unknown weak acid, and percent K and Fe in your iron salt are all determined in this way. Samples of the iron salt are run through a cation exchange column to prepare for titration. Choose either True or False for each of the following statements : A solution with a hydronium molarity of 0.00045 is acidic. pH is a way to express the hydronium concentration over a wide range.Percent K and Fe are determined by doing ion exchange then a pH titration.About 0.2M HCl is the titrant used for the pH titrations. A Lewis base is a species that can donate a proton to an acid

Answer 1

a) A solution with a hydronium molarity of 0.00045 is acidic. True

Doing the calculus of pH

`pH= -Log [H^(+)] = -Log (0.00045)`

b) pH is a way to express the hydronium concentration over a wide range. True

pH means –Log[H+] and this value is used to express a wide range of hydronium concentration sometimes obtaining pH minor than zero.

c) Percent K and Fe are determined by doing ion exchange then a pH titration. False

Usually, Fe is determined by redox titration with potassium permanganate due to it’s more accurate. On the other hand, K is determined usually by volumetric process which includes precipitation like potassium picrate precipitate

d) About 0.2M HCl is the reagent used for the pH titrations. False.

In order to do pH titration, it is possible to use a wide range of HCl concentrations and other acids as reagent if the analyte is a basic compound. Otherwise, if the analyte is an acid compound you should use a basic compound as reagent.

e) A Lewis base is specie that can donate a proton to an acid. False

A Lewis base is an electron pair donor.