Final answer:
To estimate the pH of a solution using indicators, match the observed color of the indicator to its known pH color change range. For example, methyl red is yellow above pH 4.4, suggesting that the pH of the solution is above this value if the indicator is in a yellow state.
Step-by-step explanation:
A solution's approximate pH can be determined by using pH indicators, which are substances that change color based on the pH level of the solution. Each indicator has a specific pH range where its color change occurs. To match the approximate pH of a solution given the color of various indicators, we need to understand the pH range in which each indicator changes color. The indicators mentioned in the question and their color changes are:
- Methyl orange: Red below pH 3.1 and yellow above pH 4.4
- Methyl red: Red below pH 4.4 and yellow above pH 6.2
- Bromothymol blue: Yellow below pH 6.0 and blue above pH 7.6
- Phenolphthalein: Colorless below pH 8.3 and pink above pH 10
- Alizarin yellow: Yellow below pH 10.1 and red above pH 12.0
Now, matching these indicators to the given pH conditions, we get:
- For pH > 4.4, the matching indicator would be phenolphthalein, which remains colorless.
- For pH < 8.2, the matching indicator would be bromothymol blue, which would be yellow.
- For pH < 10.1, the matching indicator could be alizarin yellow, which would be yellow.
- For pH > 6.0, methyl red would not be yellow anymore since its color change occurs up to pH 6.2.
- And for pH < 6.2, methyl red would be yellow.
Through understanding the behavior of these indicators, we are able to deduce the approximate pH of the solution based on the color changes observed.