Which alloy consists of copper and tin?

An element forms an oxide $A_{2}O_{3}$ which is acidic in nature. Identify $A$ as a metal or non-metal.

An element $A$ burns with a golden yellow flame in air. It reacts with another element $B$ (atomic number $17$) to give a product $C$. An aqueous solution of product $C$ on electrolysis gives a compound $D$ and liberates hydrogen. Identify $A$,$B$,$C$,and $D$. Also,write down the equations for the reactions involved.

Metallic oxides of zinc,magnesium,and copper were heated with the following metals. In which cases will you find displacement reactions taking place?

What are the constituent elements of Magnalium?

$(i)$ Arrange the following metals in the order of their decreasing activities: Aluminium, Gold, Sodium, Copper.
$(ii)$ Give the reaction of aluminium powder with manganese dioxide on heating.