# What are the indicators (litimus ,mythly orange ) acids ,base or neutral ?

Sep 26, 2017

It is none of them.

#### Explanation:

Because they are used to indicate if a substance is acid, base or neutral. But there is a neutral litmus paper too. But usually they are none of them.

Oct 1, 2017

Methyl orange itself is base. In general, an indicator which changes color in acid solution is base and one which changes color in base is acid.

#### Explanation:

What you should remember is that any indicator itself ($I n$, not indium in this post) has its own equilibrium point.

HIn ⇌ H^+ + In^-

Thus, the acidity constant for the indicator of the indicator ${K}_{a \left(I n\right)}$ is obtained as follows:

${K}_{a \left(I n\right)} = \frac{\left[{H}^{+}\right] \left[I {n}^{-}\right]}{\left[H I n\right]}$

When the solution has more acidity. i.e. [${H}^{+}$] goes higher,
[$I {n}^{-}$] will decrease. On the other hand, when the solution become more basic [$I {n}^{-}$] will increase.

Generally, unionized indicator $I n$ and ionized indicator $I {n}^{-}$ have diffrent color and this is how indicators works.

For example, Methyl orange changes its color from $\textcolor{red}{red} \to \textcolor{\mathmr{and} a n \ge}{\text{orange}} \to \textcolor{g o l d}{y e l l o w}$ as $p H$ changes from $3.1$ to $4.4$.

Methyl orange itself is a base since it recieves ${H}^{+}$ in low-$p H$ (strongly acid) solution.

Similar things can be said about other indicators.