Answer:
1. They can tell that a reaction has taken place if there is formation of gas bubbles in the test tube as well as if the metal dissolves in the acid solution
2. To determine which metal is more reactive, they would compare how fast each reaction occurs. The most reactive metal would have the fastest rate of reaction with a vigorous formation of bubbles, whereas the least reactive metal will have the slowest rate of reaction.
Explanation:
1. Metal which are more electropositive than hydrogen displace hydrogen from dilute acids with the formation of the salt of the metal and evolution of hydrogen gas. Therefore, the formation of gas bubbles in the test tube indicates that a reaction is taking place.
2. The rate of formation of the gas bubbles as well as the time taken for the reaction to come to a completion by the dissolution of the metal in the acid indicates which metal is more reactive. The most reactive metal would have the fastest rate of reaction with a vigorous formation of bubbles, whereas the least reactive metal will have the slowest rate of reaction.
However, the rate of the reaction is also affected by the concentration of the acid used. The higher the concentration of the acid, the faster the reaction rate.
