Question

An environmental researcher needs a carbonate buffer at pH 10.0 to study the effects of acid rain. How many grams of sodium carbonate must be added to 1.50 L of 0.200 M sodium bicarbonate to make a buffer if the Ka for sodium bicarbonate is 4.7x10-11?

Answer 1

The Henderson equation for the required buffer is used. The total volume of solution is 1.50 L and the answer is reported in 3 significant figures. See below for the step by step solution.

The reaction equilibrium required is: HCOO Laq) + 40W) = (Bicarbonate) 1. cos canst 430 (aq) i ka Carbonate Note that bicarbonate = aag & carbonate & kq = 4.7x10 = conjugate base pka = log [ 4.7x10 ") = 10.328 ; &p4=10 for buffer, using Henderson equation • ph= pk + log ( case ) pulting values values * -0.328 = wong (herein 5 (60,2-] = [nco3] x 10-03 0200x160328 M Nore that [nog]= (0,2004) given; & molar mass = 106 g/mol + [60,?] = 0.094 M Volume of solution - 1.50 L . » moles of col = 10.094 M)x (1.50 L) = 100 141 moles] = moles of Nag CO₂ mass of Nag603 = 10:14) molt x (1069/mol) 514999 Anusuvel