The graph shows the titration curve for 25.0mL of an aqueous solution of B titrated with 0.100MHCl. Which of the following best estimates the initial concentration of the solution of the weak base? (Initial pH of 12 and equivalence point at 50mL with pH of 6)
A. 0.20 M
B. 0.10 M
C. 0.067 M
D. 0.048 M
I believe it is A (since the moles are equal when there are 25ml of B and 50ml of HCl, so the molarity of B would have to be double) but I wanted someone to check my answer.
Hey there! So, we've got a titration curve, huh? Fun stuff! Now, let's crunch some numbers and get to the answers.
At the beginning of the titration (when the pH is 12), we have a weak base that hasn't reacted with any acid yet. So, it's the pure concentration of the weak base that we're looking for.
And since the equivalence point is at 50mL with a pH of 6, that means we've reached complete neutralization. At that point, all the weak base has reacted with the acid!
Now, we can use the equation: C1V1 = C2V2, which stands for concentration times volume equals concentration times volume. We'll set it up like this:
C1(25 mL) = C2(50 mL)
Since the concentration of HCl is 0.100 M, we can rewrite this equation as:
C1(25 mL) = (0.100 M)(50 mL)
Now, let's solve for C1, the concentration of the weak base:
C1 = (0.100 M)(50 mL) / 25 mL
C1 = 0.200 M
So, the initial concentration of the solution of the weak base is 0.200 M. Therefore, the best estimate from the given options would be A, 0.20 M.
Keep in mind, though, that this estimate is based on the data provided. If you're unsure or need a more accurate result, a more detailed analysis may be necessary.
I hope that helps! And remember, chemistry can be titrifyingly fun!
To find the initial concentration of the weak base, we need to analyze the titration curve and identify key points.
1. At the start of the titration (initial pH of 12), the weak base is present in excess. The pH at this point indicates that the solution is basic.
2. At the equivalence point (50 mL), the weak base has reacted completely with the acid, and the solution becomes neutral. The pH at this point is 6.
Based on this information, we can conclude that the initial concentration of the weak base should be approximately halfway between the initial pH and the pH at the equivalence point.
The initial pH is 12, and the pH at the equivalence point is 6. Taking the average of these two values gives us (12 + 6) / 2 = 9.
Since pH is a logarithmic scale of hydrogen ion concentration, we can convert it back to concentration using the formula: [H+] = 10^(-pH).
Therefore, the initial concentration of the weak base is approximately 10^(-pH) = 10^(-9) M.
Among the given choices, the closest value to 10^(-9) M is C. 0.067 M.
So, the best estimate for the initial concentration of the solution of the weak base is C. 0.067 M.
To estimate the initial concentration of the solution of the weak base, we need to use the information given in the titration curve graph.
From the graph, we can see that the initial pH is 12 and the equivalence point is at 50 mL with a pH of 6.
The initial pH of 12 indicates that the solution is basic, and as the titration progresses and more acid is added, the pH decreases.
At the equivalence point, the weak base has been completely neutralized by the strong acid, resulting in a pH of 6, which is considered neutral.
We can find the concentration of the weak base by calculating the number of moles of acid added at the equivalence point, and then dividing it by the volume of the weak base solution used.
The number of moles of acid added can be calculated using the formula:
moles of HCl = concentration of HCl × volume of HCl added
Since the concentration of HCl is 0.100 M and the volume at the equivalence point is 50 mL (or 0.050 L), we can calculate the moles of HCl added:
moles of HCl = (0.100 mol/L) × (0.050 L) = 0.005 mol HCl
Since the number of moles of HCl added is equal to the number of moles of the weak base at the equivalence point, we can calculate the initial concentration of the weak base using the formula:
initial concentration of weak base = moles of weak base / volume of weak base used
We know that the volume of weak base used is 25.0 mL (or 0.025 L), so we can calculate the initial concentration:
initial concentration of weak base = (0.005 mol) / (0.025 L) = 0.20 M
Therefore, the best estimate for the initial concentration of the solution of the weak base is 0.20 M.
Hence, the correct answer is A. 0.20 M.