Which metal oxide is used to make blue glass?

Which transition element of the $3d$ series is used in a dry battery cell?

Which one of the following is an amphoteric oxide?

Consider the following reactions:
$K_2Cr_2O_7$ $\xrightarrow[-H_2O]{KOH} [A]$ $\xrightarrow[-H_2O]{H_2SO_4} [B] + K_2SO_4$
The products $[A]$ and $[B]$,respectively,are:

Give the preparation of potassium dichromate and state its uses.
Give the structures of chromate and dichromate ions. How can chromates and dichromates be interconverted?
Give the chemical reactions showing the oxidizing nature of potassium dichromate.

Assertion : Coloured cations can be identified by borax bead test.
Reason : Transparent bead $(NaBO_2 + B_2O_3)$ forms coloured bead with coloured cation.