Imagine that

you needed to choose an indicator for the titration of a strong base (like NaOH) with a strong acid
(like HNO3). You have the indicators in Table 1 available. Which indicator would you choose? Why?

Indicator [HIn] [ In] pKa
Maryland Red- Red Blue 4.3
Terrapin Yellow -Red Yellow 7.4
Terpel Purple - Blue Red 10.5

I think terrapin yellow would be the best choice because the pH of the equivalance point in a titration of strong base with a strong acid would be pH 7.

I agree with you.

The equivalence point for a strong acid/strong base titration is 7.0; therefore you want an indicator with pKa of 7 +/- 1 or 6 as a low value and 8 has a high value. 7.4 is the only one within that range.

To choose the most appropriate indicator for the titration of a strong base (like NaOH) with a strong acid (like HNO3), you need to consider the pH range at which each indicator undergoes a color change.

In this case, the indicators given are Maryland Red, Terrapin Yellow, and Terpel Purple. Alongside each indicator, you are provided with the values of [HIn], [In], and pKa. [HIn] represents the undissociated form of the indicator molecule, [In] represents the dissociated (ionized) form of the indicator molecule, and pKa is the negative logarithm of the acid dissociation constant.

The pH at the equivalence point in a titration of a strong base with a strong acid is indeed around 7. However, it is important to choose an indicator that changes color within the pH range of the equivalence point, which is approximately pH 7.

Looking at the indicators provided, Terrapin Yellow has a pKa of 7.4. This means that Terrapin Yellow undergoes a color change around pH 7.4, which is very close to the desired pH range. The transition from red to yellow should occur in the pH range of the equivalence point, making Terrapin Yellow a suitable choice for this titration.

Therefore, Terrapin Yellow would be the preferable indicator in this scenario because it undergoes a color change within the pH range of the equivalence point for the titration of a strong base with a strong acid.