Which of the following statement$(s)$ is(are) correct when a mixture of $NaCl$ and $K_2Cr_2O_7$ is gently warmed with conc. $H_2SO_4$?

Shapes of certain interhalogen compounds are stated below. Which one of them is not correctly stated?

When $SbF_5$ reacts with $XeF_4$ to form an adduct,the shapes of cation and anion in the adduct respectively are

Which of the following statements is correct?

Sea weed is employed as a source of manufacture of

The colour of the $X_2$ molecules of group $17$ elements changes gradually from yellow to violet down the group. This is due to
[$A$] the physical state of $X_2$ at room temperature changes from gas to solid down the group
[$B$] decrease in $HOMO-LUMO$ gap down the group
[$C$] decrease in $\pi^*-\sigma^*$ gap down the group
[$D$] decrease in ionization energy down the group