Calculate the pH after 0.011 mol NaOH is added to 1.00 L of each of the four solutions.
a) 0.100 M propanoic acid (HC3H5O2, Ka= 1.3 10-5)
b) 0.100 M sodium propanoate (NaC3H5O2)
c)pure H2O
d) 0.100 M HC3H5O2 and 0.100 M NaC3H5O2
Do you have any thoughts on these at all? First you must recognize what kind of acids/bases are involved.
To calculate the pH after adding NaOH to each solution, we need to consider the acid-base reactions that occur. In the given solutions, there are different acid-base species present, so let's analyze each scenario separately.
a) 0.100 M propanoic acid (HC3H5O2, Ka= 1.3 × 10^-5):
The reaction that occurs when propanoic acid reacts with NaOH can be represented as follows:
HC3H5O2 + NaOH ⇌ NaC3H5O2 + H2O
Since NaOH is a strong base, it fully dissociates in water, meaning that the concentration of hydroxide ions (OH-) will be equal to the concentration of NaOH added.
In this case, 0.011 mol of NaOH is added to 1.00 L of a 0.100 M propanoic acid solution. To calculate the pH, follow these steps:
1. Calculate the initial concentration of propanoic acid (HC3H5O2) with the given molarity and volume:
Initial moles of HC3H5O2 = Molarity × Volume
= 0.100 mol/L × 1.00 L
= 0.100 mol
2. Calculate the moles of propanoic acid that react with NaOH. Since the ratio of propanoic acid to NaOH is 1:1, the moles of HC3H5O2 that react would be equal to the moles of NaOH added:
Moles of HC3H5O2 reacting = 0.011 mol
3. Determine the remaining moles of propanoic acid after reactiom with NaOH:
Remaining moles of HC3H5O2 = Initial moles - Moles reacted
= 0.100 mol - 0.011 mol
= 0.089 mol
4. Calculating the concentration of the remaining propanoic acid:
Remaining concentration of HC3H5O2 = Remaining moles / Volume
= 0.089 mol / 1.00 L
= 0.089 M
5. Calculate the concentration of the sodium propanoate (NaC3H5O2) formed during the reaction. Since 1 mol of propanoic acid reacts to form 1 mol of sodium propanoate, the concentration would be the same as the remaining propanoic acid:
Concentration of NaC3H5O2 = 0.089 M
6. Now, we can calculate the OH- concentration using the amount of NaOH added and dividing it by the total volume of the solution after the reaction (which is still 1.00 L):
OH- concentration = Moles of NaOH added / Volume of solution
= 0.011 mol / 1.00 L
= 0.011 M
7. Using the OH- concentration, we can calculate the pOH using the equation:
pOH = -log10 (OH- concentration)
= -log10 (0.011 M)
8. Finally, the pH can be determined using the equation:
pH = 14 - pOH
Follow these steps for the b), c), and d) solutions to calculate their respective pH values.