1. Brass gets discoloured in air because of the presence of which of the following gases in air?
2. Which of the following is a non metal that remains liquid at room temperature?
3. Chlorophyll is a naturally occurring chelate compound in which central metal is
4. The gas usually filled in the electric bulb is
5. Washing soda is the common name for
6. Quartz crystals normally used in quartz clocks etc. is chemically
7. The hardest substance available on earth is
8. The variety of coal in which the deposit contains recognisable traces of the original plant material is
9. Tetraethyl lead is used as
10. The inert gas which is substituted for nitrogen in the air used by deep sea divers for breathing, is