Answer to Question #340361 in General Chemistry for Del

Question

• Calculate the concentration of OH - ions in a 1.4 x 10^-3 M HCl solution.
• Calculate the pH of the buffer system made up of 0.15 M NH₃ and 0.35 M NH₄Cl.

Answer 1

• Calculate the concentration of OH - ions in a 1.4 x 10^-3 M HCl solution.

pOH = 14 - pH

pH = - log [HCl] = - log 1.4 x 10^-3  =2.85

pOH = 14 -2.85 = 11.15

[OH^-] = 7.08 х 10 ^-12

• Calculate the pH of the buffer system made up of 0.15 M NH₃ and 0.35 M NH₄Cl.

pOH= pK_b + log[salt]/[Acid]

 K_b of NH3 is 1.8x10^-5

pK_b= -logK_b = -log(1.8x10^-5) = 4.745

pOH= 4.745 + log(0.35/0.15) = 4.38

pH = 14 - pOH = 14 - 4.38 = 9.62