question regarding equivalence point and end point calculations:
how can i calculate the concentration of an unknown using a graph of ph values of a solution and ml of hcl? from the graph, i know that the equivalence point is 11 ml at ph 2.32.
similarly, how can i determine the concentration of the unknown using the indicator end point volume (which is 12.2ml at a ph of 1.26)
25 mL of 0.09607 M ammonia was titrated with unknown hydrochloric acid
For the NH3/HCl titration,
NH3 + HCl ==> NH4Cl
mL NH3 x M NH3 = millimols NH3.
From the equation, 1 mol NH3 = 1 mol HCl so mmols NH3 = mmols HCl
Then M HCl = mmols HCl/ml HCl used in the titration.
If I assume the 12.2 mL used with the indicator is the volume of HCl, then
(25 x 0.09607)/12.2 = M HCl
The calculation with the graph is the same but if these are for the same solutions, the agreement is lousy. Let me know if I have interpreted the question incorrectly and explain more fully.
To calculate the concentration of an unknown solution using a graph of pH values and mL of HCl, you need to understand the relationship between pH and concentration of HCl.
1. Equivalence Point Calculation:
The equivalence point is the point at which stoichiometrically equivalent amounts of acid and base have reacted. In this case, HCl is the acid and the unknown solution is the base. To calculate the concentration of the unknown solution at the equivalence point, you can use the following steps:
- Find the pH value at the equivalence point from the graph, which in this case is pH 2.32.
- Calculate the concentration of H+ ions at pH 2.32 using the formula 10^(-pH). In this case, it is 10^(-2.32).
- Since HCl is a strong acid, it fully dissociates in water, so the concentration of H+ ions is equal to the concentration of HCl.
- Calculate the moles of HCl at the equivalence point using the formula moles = concentration * volume in liters. You know the volume of HCl is 11 mL, which is equivalent to 0.011 L.
- Finally, divide the moles of HCl by the volume of the unknown solution in liters to calculate its concentration.
2. End Point Calculation:
The end point is the point at which the color change of the indicator (in this case, pH 1.26) is observed. To determine the concentration of the unknown solution at the end point using the indicator end point volume, you can follow these steps:
- Find the pH value at the end point from the graph, which is pH 1.26.
- Use the same formula as above (10^(-pH)) to calculate the concentration of H+ ions at pH 1.26.
- Calculate the moles of HCl at the end point using the formula moles = concentration * volume in liters. You know the volume of HCl is 12.2 mL, which is equivalent to 0.0122 L.
- Finally, divide the moles of HCl by the volume of the unknown solution in liters to calculate its concentration.
It's important to note that these calculations assume a 1:1 stoichiometry between the acid (HCl) and the base (unknown solution). Also, make sure to convert mL to L in the calculations by dividing by 1000.