In making gun-barrel,the steel used is

Which lanthanoid compound is used in pigments?

$X + KOH + O_2 \to Y + H_2O$,
$Y + H_2SO_4 \to Z + K_2SO_4 + MnO_2 + H_2O$
Identify $X, Y$ and $Z$ in the above reactions.

An acidified solution of potassium chromate was layered with an equal volume of amyl alcohol. When it was shaken after the addition of $1 \ mL$ of $3 \% \ H_2O_2$,a blue alcohol layer was obtained. The blue color is due to the formation of a chromium$(VI)$ compound '$X$'. What is the number of oxygen atoms bonded to chromium through only single bonds in a molecule of $X$ ?

The manganate and permanganate ions are tetrahedral,due to

Fill in the blanks:
$(1)$ ......... acid is added to perform titrations with $KMnO_4$ and $K_2Cr_2O_7$.
$(2)$ Crystals of potassium dichromate are of ......... color,while crystals of potassium chromate are of ......... color.
$(3)$ The color of $MnO_4^{2-}$ is ......... and the color of $MnO_4^-$ is ......... .