EPA acidity test can be performed by titrating water sample to a pH of 8.2. What titrant in what concentration would you suggest for EPA acidity determination?
What do you think you would use to titrate an alkaline sample? How much alkalinity do you expect to find?
To determine the acidity of a water sample using the EPA method, you need to titrate the sample to a pH of 8.2. This means you will need a titrant solution that can neutralize the acidity of the water. Here's how you can determine the appropriate titrant and its concentration for EPA acidity determination:
1. Determine the titrant: In this case, you need a strong base to neutralize the acidity of the water sample. Sodium hydroxide (NaOH) is commonly used as a titrant for this purpose because it is a strong base.
2. Calculate the titrant concentration: The concentration of the titrant solution needs to be determined based on the volume of the water sample to be titrated and the amount of acidity present. The EPA method does not provide a specific concentration recommendation, so you'll need to calculate it based on the volume and desired pH.
3. Collect the necessary information: Determine the volume of water sample you plan to titrate, as well as the expected acidity level. Let's assume you have a 100 mL water sample with an unknown acidity level.
4. Calculate the acidity in terms of milliequivalents per liter (meq/L): Convert the acidity (pH) into milliequivalents per liter, which is a unit commonly used in titrations. The conversion can be done using the equation:
Acidity (meq/L) = 10^(pH-7)
Assuming the water sample has an acidity of pH 6, the acidity can be calculated as:
Acidity = 10^(6-7) = 0.1 meq/L
5. Calculate the molar concentration of the titrant: The molar concentration of the titrant (NaOH) can be calculated using the equation:
Concentration (M) = (Acidity × Volume of water sample) / (Volume of titrant solution)
Assuming you want to prepare 100 mL of titrant solution, the concentration can be calculated as:
Concentration (M) = (0.1 × 0.1) / 0.1 = 0.1 M
Therefore, I would suggest using a 0.1 M solution of sodium hydroxide (NaOH) as the titrant for EPA acidity determination when titrating the water sample to a pH of 8.2.
My school uses this lab as well; my guess would be to use a titrant that is alkaline instead of acidic. In the alkalinity determination, the sample is titrated with an acid, lowering the pH by a specified amount. To test acidity, and raise the pH, something like NaOH should do.
As for the concentration, I would say use a concentration similar to the concentration used in your lab; we used 2x10^-3 N.