Answer:
pH = 9.11
Step-by-step explanation:
First, using gas law, we will determine the moles of NH3 bubbled. Then, with moles of HCl we can determine how many NH4⁺ are produced. As last, using H-H equation for bases we can find pOH and pH of the solution:
Moles NH3:
PV = nRT
P = pressure: 743 torr * (1atm / 760torr) = 0.9776atm
V = volume: 7.4L
n = Moles. Our incognite
R = Gas constant: 0.082atmL/molK
T is absolute temperature: 273.15K + 22°C = 295.15K
PV / RT = n
0.9776atm*7.4L / 0.082atmL*295.15K = 0.30 moles of NH3
Moles HCl:
0.50L * (0.35mol / L) = 0.175 moles of HCl
Based on the reaction:
NH3 + HCl → NH4⁺ + Cl⁻
All HCl added is producing NH₄⁺ = 0.175 moles NH₄⁺
Moles NH₃: 0.30moles NH3 - 0.175 moles = 0.125 moles NH₃
H-H equation for bases is:
pOH = pKb + log [BH+] / [B]
Where pKb = -log Kb = 4.74
[BH+] could be taken as moles of NH4+ = 0.175 mol
[B] are moles of NH3 = 0.125 mol
pOH = pKb + log [BH+] / [B]
pOH = 4.74 + log [0.175mol] / [0.125mol]
pOH = 4.89
pH = 14-pOH
pH = 9.11