To determine [H3O+] in 0.00250 M HNO2(aq)(Ka=4.5.×10−4), the first equation we would obtain in solving for x=[H3O+] isKa=[H3O+][NO2−][HNO2]=x20.00250−x Normally when x<5% Minitial, we solve this equation using the quadratic formula. This tutorial will lead you through an alternative method called successive approximations.

Now you will solve the same problem as above, but using the quadratic formula instead of iterations, to show that the same value of x is obtained either way. Using the quadratic equation to calculate [H3O+] in 0.00250 M HNO2, what are the values of a, b, c and x , where a, b, and c are the coefficients in the quadratic equation ax2+bx+c=0, and x is [H3O+]? Recall that Ka=4.5×10−4 .