stads_29

The p-nitrophenolate ion absorbs lights at 405nm. A solution that is 74um in the p-nitrophenolate ion was diluted 1 in 2 with water.Absorbance of resulting solution at 405nm was .650. Calculate molar extinction coefficient of the p-nitrophenolate ion at 405nm. Your meant to assume water has no absorbance at 405 nm. How do you use the beer lambert law to predict the absorbance at 405nm of a solution that is 11.0mM in the p-nitrophenolate ion, how do you show absorbance has no units?

Hey, have this question which i just cant wrap my head around, any help would be appreciated. Formic Acid (HCOOH) - pKa = 3.8 is a weak acid that partially dissociates to form its conjugate base (HCOO-) and releases protons into aqueous solutions. Whats the pH of a solution in which (HCOOH) = .7M and (HCOO-) = .15M? Then, if the pH of sol. of Formic acid has been titrated to a final pH of 2.8, Whats the ratio of conjugate base : Weak acid? And suppose your given stock solutions of formic acid and sodium salt of the conjugate base : (HCOOH) = 3.OM and (HCOONa) = 1.5M, How would you make a .1 M buffer(total formic acid + sodium formate concentration), 100mL total at pH 3.5, using above solutions?