What type of oxides are formed when non-metal elements combine with dioxygen gas?

An alloy has a low melting point and is,therefore,used for electrical fuses. Name the alloy and write its constituents.

Which of the following methods is used for the concentration of ore?

The composition of aqua-regia is

When a metal $X$ is treated with cold water, it gives a basic salt $Y$ with molecular formula $XOH$ (molecular mass $= 40$) and liberates a gas $Z$ which easily catches fire. Identify $X$, $Y$, and $Z$, and write the chemical reaction involved.

Which method is used to collect $H_2$ gas in a gas jar in the laboratory?