Which of the following metals is used for making jewelry?

Why do ionic compounds have high melting points? State the reason.

Which of the following gases is of brown colour?

What are the substances added to a catalyst to increase its efficiency called?

$(a)$ What type of ores are calcined? Illustrate by giving a suitable example.
$(b)$ In what form is the calcined ore obtained,and how can it be reduced? Give chemical equations of the reduction process involved for the example provided by you.
$(c)$ Name two metals used as reducing agents by displacing metals of lower reactivity from their compounds.

What is the shape of monoclinic sulphur?