Question

Calculating the composition of a buffer of a given pH . What mass of A chemistry graduate student is given 100 mL of a 0.40 M nitrous acid (HNO) solution. Nitrous acid is a weak acid with K =4.5 10 KNO, should the student dissolve in the HNO, solution to turn it into a buffer with pH = 3.46? You may assume that the volume of the solution doesn't change when the KNO, is dissolved in it. Be sure your answer has a unit symbol, and round it to 2 significant digits. X 5 ? Explanation Check 2013 McGraw-Hill Education All Rights Reserved. Puves Type here to search

Answer 1

solution As we know that for buffer solution H ₂ pka + log ( salt Given here. Ka of HNO₂ = 4.58104 [INO ] = Concentration of HNO2 = 0.4om. & pH of buffer = 3.46 Therefore pH = -log (ka) + log (salt) 3.46 = -log (4.6x10 log [.KNO2] A log {HNO2] (s: pka =_log(kes) » » 3.46 2.3.35 + log [KNO₂] 3.46 3o To.uo] log [KNO2] - 8.46-3.35 10.no] log {KNO₂] [onor = 0111 [KNO ] all =10 [0.40] [KNO₂] = 1.2980.40 2 0.516 m

Ned moles of KNO₂ = 0.516 X 100 a 0.0516 mol loos we know that No. of moles = mals molar mats i Molar mass of KNO2=85 g/mol in mass of KNO2 z 0.0516885 = 4.386 g ~ 4.4 g Ans.)