In a blast furnace,what prevents the oxidation of molten iron?

What happens to potassium and sodium if they are kept in the open? Why are they immersed in kerosene?

Account for the following:
$(a)$ Aluminium is more reactive than iron,but its corrosion is less than iron.
$(b)$ Hydrogen gas is not evolved when zinc metal reacts with dilute $HNO_3$.
$(c)$ Carbon is not used for reducing aluminium from aluminium oxide.

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

$(i)$ Arrange the following metals in the order of their decreasing activities: Aluminium, Gold, Sodium, Copper.
$(ii)$ Give the reaction of aluminium powder with manganese dioxide on heating.

What is the chemical formula for potassium dichromate?