Which metal can be beaten into very thin foils?

Which of the following is a dibasic acid?

What is the molecular formula of calcium silicate (slag)?

$A$ metal $M$ does not liberate hydrogen from acids but reacts with oxygen to give a black coloured product. Identify $M$ and the black coloured product,and also explain the reaction of $M$ with oxygen.

$(i)$ Explain the steps for extraction of copper from its sulphide ore. Write the balanced equations involved in the process.
$(ii)$ What is meant by refining of metals? Draw a diagram of electrolytic refining of copper and name the substances used as cathode, anode, and the electrolyte.

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

$X$	$Y$
$1.$ Dehydrating agent	$p.$ Sulphur dioxide gas
$2.$ In preparation of firecrackers	$q.$ Concentrated sulphuric acid
$3.$ Weak bleaching agent	$r.$ Dihydrogen gas
$4.$ Lightest gas	$s.$ Sulphur