Question

4. A volume of 30.0 mL of 0.10 M NH, (aq) is titrated with 0.20MCThe value of the base-dissociation (aq) constant, K, for HCO2 in water is 1.2 x 1010 at 25°C. a. (1 pt.) Write the ionic equation for the reaction of NH, (aq) with HCL(aq) (1 pt.) What is the volume of base added at the equivalence point? Show work or reasoning. b. (1 pt.) Will the pH of the equivalence point be higher than, lower than or equal to 7? c. 12 d. (1 pt.) What is the pH and pOH at the half equivalence point? 10 (4 pts.) Using the axes provided, sketch the titration e. curve that results when a total of 40.0 mL of 0.20 M HCI(aq) is --t- t-- added drop wise to the 30.0 mL volume of 0.10 M NH, (aq) 40 20 30 10 (2 pts) From the table below, select the most f. appropriate indicator for the titration. Justify your choice. pKa 5.5 Bromothymol Blue7.1 Phenolphthalein 8.7 Indicator Methyl Red (3 pts.) Consider the following potential sources of error in the titration lab: g. l. If there was a little distilled water in the Erlenmeyer flask before the titration began, how would the final molarity of the NH, be affected? Explain. Il. If the buret had been rinsed before the titration was started with distilled water and some drops were left in it when it was filled with the HCI, how would the final molarity of the NH, be affected? Explain. IIl Some HCl solution dripped into the Erlenmeyer flask before the initial HCI volume was measured, how would the final molarity of the NH, be affected? Explain.

Answer 1

a. NH3+HCl->NH4+Cl-

b.volume neede is 15 ml according to N1V1=N2V2

c.ph will be higher than 7