Which of the following ores is in the form of oxide?

In the electrolytic refining of copper metal,which of the following decreases in weight?

What is formed when boiling sulfur reacts with dihydrogen gas?

What is the color of a potassium dichromate solution?

Name two metals which have very low melting points.

Provide one exception for each of the following general statements:
$(i)$ Metals are lustrous.
$(ii)$ Metals are solids at room temperature.
$(iii)$ Metals have high melting points.
$(iv)$ Non-metals are non-lustrous.
$(v)$ Non-metals are insulators or non-conductors of electricity.