Test-exam 2

A the student should select 440nm and 625nm as the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: s that HCl absorbs light strongly near 440nm but weakly around 625nm. c. The bcg primarily exists in the basic form (i.e., In ) in flask 1. d. Where the two curves cross, [ HIn] [ In ] . e. For flask 8, near 440-nm, the bcg exists in the protonated form, HIn . 7 10. Which of the following combinations of substances will give a buffered solution that has a pH of 5.05? (Assume each pair of substances is dissolved in 5.0 L of water. Also, given that a. b. c. d. K b 1.8 105 for NH 3 , K b 1.7 109 for C5 H 5 N , K w 1.0 1014 for H 2O , K a Kb K w ) 1.0 mole NH 3 and 1.5 mole NH 4C 1.5 mole NH 3 and 1.0 mole NH 4C 1.0 mole C5 H 5 N and 1.5 mole C5 H 5 NHC * 1.5 mole C5 H 5 N and 1.0 mole C5 H 5 NHC e. none of the above. Ans. For NH3, K w 1.00 1014 Ka 5.56 1010 , pK a 9.25 5 Kb 1.8 10 For C5H5N, K w 1.00 1014 Ka 5.88 106 , pK a 5.23 9 Kb 1.7 10 Therefore we need to consider only c or d. Rearrange the HH equation, pH pK a log [ Base] [ Base] [ Base] , l og 10 pH pKa pH pK a , [ Acid ] [ Acid ] [...
View Full Document

This note was uploaded on 03/03/2011 for the course CHEM 100A taught by Professor Dai during the Spring '06 term at UCSD.

Ask a homework question - tutors are online