Can someone please help me on this two Chemistry questions...they are from my lab....the lab was on Acids and Bases using Red Cabbage Indicator.
Q1- How consistent was the cabbage juice indicator for this lab? Discuss the limitations of using red cabbage juice as an indicator in comparison to the universal pH paper?
The first part of the question I know but it's the second part that I am stuck on!
Q2- What is the relationship (i.e. direct or inverse) between pH and hydrogen ion concentration? Remembering that pH= -log[H+]. Please explain.
Thanks so much for the help ;-) Online chemistry is so hard!
On q1. pH paper can tell pHs over a wide range, rather accurately. Did the Cabbage juice do that?
How consistent was the cabbage juice indicator for this lab? Discuss the limitations of using red cabbage juice as an indicator in comparison to the universal pH paper.
Q1- How consistent was the cabbage juice indicator for this lab? Discuss the limitations of using red cabbage juice as an indicator in comparison to the universal pH paper.
To determine how consistent the cabbage juice indicator was in the lab, you can compare the results obtained from different trials or measurements. If the color change from the cabbage juice indicator was consistent across all trials and matched with the expected pH values, then the indicator was considered consistent for that specific lab.
Some limitations of using red cabbage juice as an indicator in comparison to universal pH paper include:
1. Sensitivity: Universal pH paper is more sensitive than red cabbage juice. It can detect small changes in pH, whereas the color changes in the cabbage juice may be less pronounced or less accurate.
2. Precision: Universal pH paper provides a more precise and quantifiable measurement of pH as it has a numerical scale. On the other hand, the color changes in red cabbage juice indicators are subjective and can differ based on human perception.
3. Range: Universal pH paper covers a wider pH range, typically from 1-14, whereas red cabbage juice indicators have a more limited range, usually optimal within the pH range of 3-7.
4. Calibration: Universal pH paper is factory-calibrated, which ensures accuracy and consistency. In contrast, the red cabbage indicator might require preparation and calibration by the laboratory technician, making it prone to inaccuracy if not appropriately calibrated.
Considering these limitations, universal pH paper is often preferred in scientific settings due to its precision, sensitivity, wide range, and ease of use.
Q2- What is the relationship (i.e., direct or inverse) between pH and hydrogen ion concentration? Remembering that pH = -log[H+]. Please explain.
The relationship between pH and hydrogen ion concentration is inverse. The pH scale is a logarithmic scale that measures the acidity or alkalinity of a solution. The pH value is determined using the equation pH = -log[H+], where [H+] represents the hydrogen ion concentration.
In this equation, "-" indicates that the pH is inversely proportional to the logarithm of [H+]. This means that as the [H+] increases, the pH decreases, indicating a more acidic solution. Conversely, as the [H+] decreases, the pH increases, indicating a more alkaline (basic) solution.
For example, if the hydrogen ion concentration is 10^-3 M (moles per liter), the pH would be calculated as follows:
pH = -log(10^-3) = -(-3) = 3
This calculation shows that a higher hydrogen ion concentration corresponds to a lower pH value, indicative of higher acidity.
In summary, as the hydrogen ion concentration decreases, the pH increases, reflecting a more basic solution. As the hydrogen ion concentration increases, the pH decreases, indicating a more acidic solution.