Which solution is used as an electrolyte in a Voltaic cell?

What is formed when sodium absorbs moisture from air? Give the chemical equation as well.

Which metal is more reactive than magnesium $(Mg)$?

$A$ man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?

Write equations for the reactions of:
$(i)$ Iron with steam
$(ii)$ Calcium and potassium with water

Which of the following is used for the dissolution of gold?