Which of the following salts does not produce nitrogen dioxide $(NO_2)$ upon heating?

In the isoelectronic series of metal carbonyls,the $CO$ bond strength is expected to increase in the order:

$Fe_2Cr_2O_4 + Na_2CO_3 + O_2$ $\xrightarrow{\text{Fusion}} [X]$ $\xrightarrow{H^+ / H_2O} [Y]$ $\xrightarrow{H_2O_2 / H^+} [Z]$
Which of the following statements is true for the compounds $[X], [Y],$ and $[Z]$?

What is the reduction electrode potential (in volts) of a copper electrode when $[Cu^{2+}] = 0.01 \ M$ is in a solution at $25^{\circ} C$? ($E^{\circ}$ of $Cu^{2+}/Cu$ electrode is $+0.34 \ V$)

If $[2,6]$ is divided into four intervals of equal length, then the approximate value of $\int_2^6 \frac{1}{x^2-x} dx$ using Simpson's rule is

What does orthoboric acid contain?