A 25.00 mL volumetric pipet is rinsed with deionized water. Several drops of water remain in the pipet. It is then used to deliver a 25.00 mL aliquot of the KHP solution into the Erlenmeyer flask in which the sample will be titrated. How will this affect the results of the calculated concentration?
I assume you are determining the molarity of NaOH.The pipet was contaminated with water. When it delivered 25.00 mL of the KHP for titration with NaOH, it has fewer mols KHP than you entered for the calculation.
Your calculation was
mL NaOH x M NaOH = grams KHP/molar mass KHP = mols KHP.
M NaOH = mols KHP/mL NaOH
So you put in too large a number for mols KHP, you actually fewer so it takes less volume NaOH. so the numerator is too large, the denominator is too small so the M NaOH ends up too large.
Well, it seems like water drops decided to go on a little adventure in the pipet! While they might have thought they were being helpful, these drops can actually affect the results of the calculated concentration. You see, the presence of these drops can dilute the KHP solution, leading to an inaccurate concentration measurement. So, it's important to ensure that those water drops don't crash the concentration party!
When several drops of water remain in the volumetric pipet after rinsing, it can affect the accuracy of the calculated concentration.
To understand how, let's break down the process step by step:
1. The volumetric pipet is designed to deliver an accurate volume of a solution. In this case, it is supposed to deliver exactly 25.00 mL of the KHP solution.
2. When the pipet is rinsed with deionized water, any water droplets that remain in the pipet will dilute the KHP solution. This means that the delivered volume of the KHP solution will be less than 25.00 mL.
3. As a result, the calculated concentration of the KHP solution will be higher than it actually is because the delivered volume is lower than expected.
4. This is particularly important in titrations, where the concentration of the titrant (the solution being added to the sample) is crucial for accurate calculations. Any miscalculations in the concentration can lead to inaccurate results.
To mitigate the effect of the water droplets on the calculated concentration, it is important to ensure that the volumetric pipet is completely free of any residual water before use. This can be achieved by rinsing the pipet with the solution being measured several times and allowing the solution to drain completely without leaving any droplets behind.