A solution is made by mixing 25 mL of .35 M LiOH with 15.5 mL of .2225 M NH3. Kb=1.8x10^-5 for NH3
Calculate the pH for the solution.
To calculate the pH of the solution, we need to first determine the concentration of OH- ions in the solution, and then use that information to calculate the pOH. Finally, we can convert the pOH to pH using the equation pH = 14 - pOH.
Let's start by calculating the amount of OH- ions present in the solution by using the following equation:
LiOH(aq) → Li+(aq) + OH-(aq)
From the balanced equation, we can see that for every mole of LiOH, we will get one mole of OH- ions. Therefore, we need to determine the number of moles of LiOH in the solution.
The concentration of LiOH is given as 0.35 M, and the volume is given as 25 mL. We can convert the volume from milliliters to liters by dividing by 1000:
Volume = 25 mL = 25/1000 = 0.025 L
Now, we can calculate the moles of LiOH using the equation:
Moles of LiOH = concentration × volume
= 0.35 M × 0.025 L
= 0.00875 moles
Since LiOH and NH3 react in a 1:1 ratio, the moles of OH- ions in the solution are equal to the moles of LiOH. Therefore, we have 0.00875 moles of OH- ions.
Now, let's calculate the moles of NH3 in the solution. The concentration of NH3 is given as 0.2225 M, and the volume is given as 15.5 mL. Converting the volume to liters:
Volume = 15.5 mL = 15.5/1000 = 0.0155 L
Moles of NH3 = concentration × volume
= 0.2225 M × 0.0155 L
= 0.00344575 moles
Since NH3 reacts with OH- ions, we need to compare the moles of OH- ions with the moles of NH3. In this reaction, they are in a 1:1 ratio, so we have an excess of OH- ions.
To calculate the concentration of the OH- ions, we divide the moles by the total volume of the solution:
Total volume = volume of LiOH + volume of NH3
= 0.025 L + 0.0155 L
= 0.0405 L
Concentration of OH- ions = Moles of OH- ions / Total volume
= 0.00875 moles / 0.0405 L
= 0.2154 M
Now that we have the concentration of OH- ions, we can calculate the pOH using the equation:
pOH = -log[OH-]
= -log[0.2154]
= 0.6686
Finally, we can calculate the pH using the equation:
pH = 14 - pOH
= 14 - 0.6686
= 13.3314
Therefore, the pH of the solution is approximately 13.3314.