Brass gets discoloured in air because of the presence of which of the following gases in air?

A. Oxygen
B. Hydrogen sulphide
C. Carbon dioxide
D. Nitrogen


Which of the following is a non metal that remains liquid at room temperature?

A. Phosphorous
B. Bromine
C. Chlorine
D. Helium


Which of the following is used in pencils?

A. Graphite
B. Silicon
C. Charcoal
D. Phosphorous


Chlorophyll is a naturally occurring chelate compound in which central metal is

A. copper
B. magnesium
C. iron
D. calcium


Which of the following metals forms an amalgam with other metals?

A. Tin
B. Mercury
C. Lead
D. Zinc