Final answer:
To obtain a buffer solution with a pH of 9.36 using ammonia and ammonium chloride, you need to add 0.581 grams of ammonium chloride to 2.35 liters of a 0.150 M NH3 solution.
Step-by-step explanation:
To calculate the mass of ammonium chloride needed to obtain a buffer solution with a pH of 9.36, we need to use the Henderson-Hasselbalch equation for a weak base buffer solution. The equation is pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the conjugate base and [HA] is the concentration of the acid.
In this case, ammonia (NH3) is the weak base and ammonium chloride (NH4Cl) is the conjugate acid.
First, we need to find the pKa of the conjugate acid NH4+. Since Kb is given as 1.76x10^-5, we can use the equation pKa + pKb = 14 to find pKa, which is 14 - pKb = 14 - (-log(Kb)) = 14 - (-log(1.76x10^-5)) = 9.75.
Next, we can substitute the values into the Henderson-Hasselbalch equation: 9.36 = 9.75 + log([A-]/[HA]). Solving for [A-]/[HA], we find that it is 10^-0.39. Since [A-]/[HA] is equal to the ratio of moles of NH3 to moles of NH4Cl, we can set up an equation using the molar mass of NH4Cl to find the mass of NH4Cl needed. Therefore, the mass of NH4Cl needed is 0.150 x 2.35 x (10^-0.39) x (53.49 g/mol) = 0.581 grams.