Question

Calculate the concentration of buffer components present in 217.00 mL of a buffer solution that is 0.270 M NH4Cl and 0.270 M NH3 after the addition of 2.10 mL of 6.0 M HNO3.

[NH3] = ___ M

[NH4+] = ____ M

Answer 1

mol of HNO3 added = 6.0M *2.1 mL = 12.6 mmol

NH3 will react with H+ to form NH4+

Before Reaction:

mol of NH3 = 0.27 M *217.0 mL

mol of NH3 = 58.59 mmol

mol of NH4+ = 0.27 M *217.0 mL

mol of NH4+ = 58.59 mmol

after reaction,

mol of NH3 = mol present initially - mol added

mmol of NH3 = (58.59 - 12.6) mmol

mol of NH3 = 45.99 mmol

mol of NH4+ = mol present initially + mol added

mol of NH4+ = (58.59 + 12.6) mmol

mol of NH4+ = 71.19 mmol

total volume = 217 + 2.10 = 219.10 mL

[NH3] = 45.99 mmol / 219.10 mL

= 0.2099 M

[NH4+] = 71.19 mmol / 219.10 mL

= 0.3249 M

[NH3] = 0.2099 M

[NH4+] = 0.3249 M