0.5 L of a 0.30 M HCl solution is titrated with a solution of 0.6 M KOH.
a)What is the pH before addition of KOH?
b)What is the total number of moles of acid?
c)What is the pH after addition of 125 mL of KOH solution?
d)What volume of the KOH solution is required to reach the equivalence point?
e)What is the pH at the equivalence point?
f)What is the pH after addition of 375 mL (total) of KOH solution?
The secret to working these problems is to know where you are on the titration curve and solve accordingly.
a) At the beginning, you have pure HCl.
b) moles = M x L
c) moles KOH = M x L. Subtract from moles HCl initially. The difference is the moles HCl left.
d) moles HCl = moles KOH
e) What salt do you have at the equivalence point? That's NaCl, the salt of a strong acid and strong base. The pH is determined by the hydrolysis of the salt.
f) moles KOH = M x L. Subtract moles HCl. The difference is the moles KOH in excess (note the difference between this and part (c).
For part a, would the pH be .523?
I still don't understand part e.
Im lost, I don't think Im doing any of it right :/
9.8
To answer these questions, we need to perform calculations based on the given information and the concepts of acid-base titrations. Let's go through each question one by one:
a) What is the pH before the addition of KOH?
Before the addition of KOH, we have a solution of HCl, which is a strong acid. The pH of a strong acid solution can be found using the formula pH = -log[H+], where [H+] represents the concentration of H+ ions.
In this case, the concentration of HCl is given as 0.30 M. Therefore, before the addition of KOH, the concentration of H+ ions is also 0.30 M. Substituting this value into the formula, we get: pH = -log(0.30)
To find the pH, you can use a scientific calculator to calculate the log of 0.30 and then multiply the result by -1.
b) What is the total number of moles of acid?
To calculate the total number of moles of acid, we need to multiply the volume of the HCl solution (0.5 L) by its concentration (0.30 M):
Total moles of acid = Volume x Concentration
= 0.5 L x 0.30 mol/L
c) What is the pH after the addition of 125 mL of KOH solution?
To determine the pH after the addition of the KOH solution, we need to determine the number of moles of HCl that reacted with the KOH. This can be achieved by using the equation:
Moles of HCl reacted = Moles of KOH added
Here, we know the volume (0.125 L) and concentration (0.6 M) of the KOH solution. By multiplying the volume by the concentration, we can determine the number of moles of KOH added. Then, we can use stoichiometry to determine the moles of HCl reacted.
Once we know the moles of HCl reacted, we can calculate the remaining moles of HCl and find the new concentration. With the new concentration, we can then calculate the new pH using the same formula as in part (a).
d) What volume of the KOH solution is required to reach the equivalence point?
The equivalence point is reached when the moles of acid are equal to the moles of base (in this case, KOH). To calculate the volume, we need to use stoichiometry.
First, determine the number of moles of acid in 0.5 L of 0.30 M HCl using the formula from part (b).
Next, we need to determine the number of moles of KOH required to react with the HCl. This can be done using the balanced chemical equation between HCl and KOH.
Finally, convert the moles of KOH into volume (in liters) by dividing the number of moles by the concentration of KOH (0.6 M).
e) What is the pH at the equivalence point?
The equivalence point occurs when the moles of acid and the moles of base are stoichiometrically balanced. For a strong acid-strong base titration like this one, the pH at the equivalence point is 7, indicating a neutral solution.
f) What is the pH after the addition of 375 mL (total) of KOH solution?
To determine the pH after the addition of 375 mL of KOH solution, we follow a similar method to part (c). We calculate the moles of KOH added by multiplying the volume (375 mL or 0.375 L) by the concentration (0.6 M). Then, we use stoichiometry to determine the moles of HCl that reacted with the KOH. Finally, we calculate the remaining moles of HCl, find the new concentration, and use the formula from part (a) to find the new pH.
Remember to perform the necessary calculations step by step for accurate results.