Question

What is the pH of the buffer solution that contains 1.9 g of NH4 Cl in 250 mL of 0.13 M NH3? Is the final pH lower or higher than the pH of the 0.13 M ammonia solution? ( for ammonia is.) pH of the buffer = The final pH is _______higherlower than the pH of the 0.13 M ammonia solution.

Answer 1

Number of moles of NH4CI mass/mol.wt. 1.9 g/(53.491 g/mol) 0.03552 mol Number of moles of NH3 = M*V = 0.13 M * 0.250 L 0.0325 mol The pH of the buffer is [асid] РОН — рКb +1og [base] 0.03552 pOHlog (1.8x10)log 0.0325 pOH 4.745+0.03859 = 4.783 PH — 14— рОН —14—4.78- 9.22

Given that concentration of NH3 3D 0.13 М Kb of NH3 1.8 x 10-5 Къ м NH2 NH3 + H,о ОН Initial 0.13 0 0 Change X -х Equillibrium 0.13 -X х.х 1.8x10-5 0.13-x x2-1.8x10x-2.34 x106 = 0 by solving we get x 0.001521 .[OH]x= 0.001521M pOH log(0.001521) 2.82| pH 14-2.82 11.18 pH of the buffer solution is lower than that of pH of 0.13 M ammonia solution + X