The equivalent weight of $Na_2S_4O_6$ in the reaction $2Na_2S_2O_3 + I_2 \to Na_2S_4O_6 + 2NaI$ is :-

Phenolphthalein does not act as an indicator for the titration between

The set of coefficients of $P_4$,$OH^{\Theta}$ and $H_2PO_2^{\Theta}$ in the balanced reaction $P_4 + OH^{\Theta} \to PH_3 + H_2PO_2^{\Theta}$ is

What is the number of electrons transferred considering $Mn$ when $KMnO_4$ is converted into $Mn_2O_3$?

Balance the following redox reactions using the oxidation number and ion-electron method:
$(1) H_2S + Fe^{3+} \to Fe^{2+} + S + H^{+}$
$(2) Cu + NO_3^{-} \to Cu^{2+} + NO_2$
$(3) Sn + NO_3^{-} + H^{+} \to Sn^{2+} + NH_4^{+} + H_2O$
$(4) As + NO_3^{-} + H^{+} \to AsO_4^{3-} + NO_2 + H_2O$

Which among the following species acts as a self-indicator?