I have data for titration of a strong base against a strong acid when I added volumes of NaOH 1 mL at a time to 50.00 mL of HCl to see the change in pH.
One of the questions says to find the molarity of the HCl solution but how do I do this with the data.
There are two ways, one is an estimate and the other is exact.
For the estimate, look at the pH values. When the pH changes from low numbers (you said you were titrating HCl by adding 1 mL portions of NaOH) to high numbers (pH 2 or 3 to pH 9 or 10), the equivalence point is between those two values of NaOH. Then mL x M = mL x M and solve for M NaOH.
The exact way is not nearly that easy. Take the second derivative of the additions, plot the second derivative of pH versus mL. The pH will curve will change sharply from a high number to aa low number. Where the line crosses the zero point is the mL for the equivalence point. See if that method is described in your text.
To find the molarity of the HCl solution, you need to use the balanced chemical equation for the reaction between HCl and NaOH. The balanced equation is:
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
From the balanced equation, you can see that the mole ratio between HCl and NaOH is 1:1. This means that one mole of HCl reacts with one mole of NaOH.
Here's how you can find the molarity of the HCl solution using the given data:
1. Convert the volume of NaOH used to moles: Since you added 1 mL of NaOH at a time, you need to find the number of moles of NaOH in each addition. To do this, divide the volume of NaOH used (in mL) by 1000 to convert it to liters, and then multiply it by the molarity of NaOH. Let's say the molarity of NaOH is M NaOH. Then the number of moles of NaOH added in each step is:
moles of NaOH = (Volume of NaOH used / 1000) × M NaOH
2. Use the mole ratio from the balanced equation: Since the mole ratio between HCl and NaOH is 1:1, the same number of moles of HCl react with NaOH. So the number of moles of HCl in each addition is also:
moles of HCl = moles of NaOH
3. Calculate the total number of moles of HCl: Add up the moles of HCl from each addition to find the total number of moles of HCl.
4. Calculate the molarity of the HCl solution: Divide the total number of moles of HCl by the volume of HCl used (50.00 mL converted to liters):
Molarity of HCl = (Total moles of HCl) / (Volume of HCl used / 1000)
By following these steps and using the given data, you should be able to find the molarity of the HCl solution.