Which gas is produced when zinc reacts with diluted hydrochloric acid?

Which of the following is a noble metal?

An element $A$ is soft and can be cut with a knife. It is very reactive to air and cannot be kept open in air. It reacts vigorously with water. Identify the element from the following:

Food cans are coated with tin and not with zinc because

Which among the following alloys contains mercury as one of its constituents?

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