$X + H^{+} \rightarrow Y + Na^{+} + H_2O$
$Y + KCl \rightarrow K_2Cr_2O_7 + NaCl$
Identify $X$ and $Y$ in the given reactions.

In ruby and emerald,the metal ion$(s)$ present is/are

Which of the following elements is doped into a fiber amplifier in an optical fiber communication system?

Given below are some statements about $Mn$ and $Mn_2O_7$. Identify the correct statements:
$A$. $Mn$ forms the oxide $Mn_2O_7$ in which $Mn$ is in its highest oxidation state.
$B$. Oxygen stabilizes the $Mn$ in higher oxidation states by forming multiple bonds with $Mn$.
$C$. $Mn_2O_7$ is an ionic oxide.
$D$. The structure of $Mn_2O_7$ consists of one bridged oxygen.
Choose the correct answer from the options given below:

One of the important uses of ferrous sulphate is in the

$K_2Cr_2O_7$ on heating with aqueous $NaOH$ gives: