Which alloy is used to prepare scientific balance?

What are the constituent elements of Magnalium?

Make the correct pairs from below mentioned $'X'$ and $'Y':$

$1. \text{Sulphurous acid}$	$p. H_{3}PO_{4}$
$2. \text{Sulphuric acid}$	$q. H_{2}S_{2}O_{7}$
$3. \text{Oleum}$	$r. H_{2}SO_{3}$
$4. \text{Phosphoric acid}$	$s. H_{2}SO_{4}$

Which of the following is $NOT$ the correct order of reactivity of metals?

Name the following:
$(a)$ $A$ metal which is preserved in kerosene.
$(b)$ $A$ lustrous coloured non-metal.
$(c)$ $A$ metal which can melt while kept on palm.
$(d)$ $A$ metal which is a poor conductor of heat.

Which of the following gases acts as a mild bleaching agent?