pH When the Concentration of Added Acid or Base in the Solution is Less than 10^
ID: 950932 • Letter: P
Question
pH When the Concentration of Added Acid or Base in the Solution is Less than 10^-6M (Ch.8, s. 1) What is the pH of 1 x10 -8 M HCl What is the pH of 1 x10 -8 M NaOH If pH 7 is neutral and pH 7 is basic are your findings above correct When the concentration of added strong acid or base is less than 1 x10^-6 M it is similar in value to the natural concentration of dissociated H^+ or OH^- in water and the new equilibrium concentrations need to be found to calculate the correct pH. What we need to solve this is K_w, and the fact that [Na^+]=10^_8M. By the balance of charge in the solution [OH^-] = [H^+] + [Na^+]. With these three equations find the correct pH.Explanation / Answer
Since it is HCl solution (HCl in water of neutral pH), water also undergoes ionization
Hence H2O---> H+ +OH- and HCl--->H+ +Cl-
hence pH= 10-8 (HCl)+10-7 (Neutral water)= 10-7*(1+0.1)= 1.1*10-7M
pH= -log (1.1*10-7)=6.958
b) [OH-] =10-8+10-7= 1.1*10-7, pOH= 6.958
pH= 14-6.958=7.042
17 if PH<7 it is acidic, pH=7 it is neutral and pH>7, it is basic.
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