The element which forms oxides in all oxidation states from $+I$ to $+V$ is

What is the maximum concentration of aqueous $HNO_3$ that can be obtained by distillation with concentrated $H_2SO_4$ in terms of percentage by mass (in $\%$)?

In which of the following options do all species contain $X-O-X$ bonds in their structure ($X =$ central atom)?

When dilute $H_2SO_4$ is added to dry $KNO_3$,brown fumes are evolved. What are these brown fumes?

Match List $I$ with List $II$:

List $I$ Oxide	List $II$ Type of Bond
$A. N_2O_4$	$I. 1 N-O$ bond
$B. NO_2$	$II. 1 N-O-N$ bond
$C. N_2O_5$	$III. 1 N-N$ bond
$D. N_2O$	$IV. 1 N=N / N\equiv N$ bond

Choose the correct answer from the options given below:

When aluminium phosphide is treated with dil. sulphuric acid,which gas is evolved?