Hi, so I did a lab on acids, bases, salts and buffer solutions. After measuring the pH for a .010 M HCl solution I got a pH of 2.50. After doing a calculated pH of .010 M of HCl the answers is 2.
My question is why do you think my pH from the experimental is slightly higher than that of the calculated? And is this .5 difference really that significant?
Thanks!
Why? There may be several reasons.
1. The pH meter wasn't standardized properly; i.e., it could have been set at pH 7 or 8 but you were measuring 2. It does happen from time to time;I have done it myself.
2. The temperature of the solution measured was not the same as the standardizing soln. This robably is not a factor here.
3. Your calculations are done with concentrations in moles/L whereas the 0.01M does not have an activity of 0.01. This is the most probable reason but would not account for more than about 0.1 (meaning soln with pH 2.0 would measure about 2.1 or so).
4. The SCE or glass electrode could be faulty. That has happened to me, too.
Is it significant? That all depends upon what you are doing. Some cases yes and some no.
Thank you for your feed back it helped me out greatly!
The slight difference between the experimental pH of 2.50 and the calculated pH of 2 for a 0.010 M HCl solution could be attributed to several factors. Here are a few possibilities:
1. Measurement error: pH measurements are sensitive and can be influenced by various factors, such as the accuracy of the pH meter or the technique used to measure the pH. Small errors in measurement can lead to differences between the experimental and calculated values.
2. Presence of impurities: The experimental HCl solution might contain impurities or other substances that affect its pH. These impurities can contribute to a higher measured pH.
3. Dissociation behavior: The calculation of pH assumes complete dissociation of HCl into H+ and Cl- ions, which is a simplification. In reality, not all HCl molecules dissociate completely. There could be a slight decrease in the concentration of H+ ions due to incomplete dissociation, leading to a slightly higher pH value.
Regarding the significance of the 0.5 difference in pH, it depends on the context and the specific application. In some cases, this difference can be considered relatively small and not significant. However, in other instances, such as precise scientific experiments or industrial processes, even small deviations can have practical implications and might require further investigation.
To verify the accuracy of your pH measurements, you can perform additional replicates of the experiment and calculate the average pH. Additionally, you could use a different method or pH indicator to measure the pH, which may help confirm the consistency of your results.