The gas that is the most dangerous pollutant to human is

Which of the following alloys contain iron?

In a flame test for calcium, the flame appears

The most abundant element on the earth's crust is

N2(g) + 3H2(g) ↔ 2NH3(g) ΔH = -90 kJ In the equation above, the yield of ammonia can be decreased by

To obtain pure carbon (II) oxide from its mixture with carbon (IV) oxide, the mixture should be

Metalliods are also referred to as

The ores that can be concentrated by flotation are

The property used in the industrial preparation of nitrogen and oxygen from air is