Hi there. I'm doing a paper on Biology (yes I know, will explain the chem link in a sec) and in it am trying to find the best pH level for Slaters, using limewater and filtered water to change concentrations. I have done experiments and using bunch of ratios (eg 2 parts limewater: 1 part water. What I want to know is: if you know the concentration of the limewater and water used, and the exact amount used, is it possible to calcualate pH using that? And how would I go about doing it?
Many thanks,
JB
The calculations will be affected a lot by what is in the water already (I assume it is not pure water). You should be testing the water lime mixture for pH, testing is easy with pH paper, and accurate. Any living thing in water affects the pH also, especially with its waste products.
Test the water pH, don't depend on the "calculated"value to be the real pH.
Hi JB! It's great that you're conducting experiments for your biology paper. Calculating the pH using the concentration and amount of limewater and water used is indeed possible. To do so, you would need to know the concentration of limewater in terms of moles per liter (Molarity) and apply the concept of dilution.
Here are the steps to calculate the pH using the given information:
1. Determine the moles of the substance (limewater or water) using the given concentration and volume.
- For example, if the concentration of limewater is 0.1 M and the volume used is 100 mL (0.1 L), you would have:
Moles of limewater = 0.1 M x 0.1 L = 0.01 moles.
2. If both limewater and water are mixed together, you need to calculate the total volume of the resulting solution.
- Using your example of a 2:1 ratio, if you use 2 parts (limewater) and 1 part (water), the total volume would be 3 parts.
- If each part is 100 mL, then the total volume would be 300 mL (0.3 L).
3. Determine the moles of the resulting solution using the total volume calculated.
- Moles of resulting solution = (Moles of limewater + Moles of water) = 0.01 moles + 0 moles (since water does not contribute to moles) = 0.01 moles.
4. Calculate the concentration of the resulting solution in terms of moles per liter (Molarity).
- Concentration = Moles of resulting solution / Total volume in liters.
- Concentration = 0.01 moles / 0.3 L = 0.0333 M (rounded to 4 decimal places).
5. Finally, you can use the concentration to calculate the pH using the Henderson-Hasselbalch equation for weak acids and bases.
- pH = pKa + log [A-] / [HA]
- Since limewater is slightly basic, you will need the pOH, which is related to pH as pH + pOH = 14.
- Determine the pKa value for limewater and plug in the appropriate concentrations to calculate the pH.
Please note that this method assumes that limewater acts as a pure acid or base and does not consider other factors that may affect the system. Additionally, using an experimental measurement of the pH using a pH meter or indicator paper would provide more accurate results.
I hope this helps! Let me know if you have any more questions.