Question

Which element will reduce Mg2+ to Mg?
a) Fe b) Ba c) Pb d) Ag

Answer 1

The correct answer is Ba (barium), as it is more reactive than Mg (magnesium) and, according to the activity series, can reduce Mg2+ to Mg. So the correct option is b.

Step-by-step explanation:

To determine which element will reduce Mg2+ to Mg, we need to consider the relative reactivity of the elements involved. In a reduction-oxidation (redox) reaction, a more reactive metal can displace a less reactive one from its compound. The relative reactivities of the metals given can be found in the activity series, which is a list of metals arranged in order of decreasing reactivity.

According to the activity series, which typically places magnesium below barium and above iron, lead, and silver, we can conclude that:

• Barium (Ba) is more reactive than magnesium (Mg), so it can reduce Mg2+ to Mg.
• Iron (Fe), lead (Pb), and silver (Ag) are less reactive than magnesium and therefore cannot reduce Mg2+ to Mg.

Therefore, the correct answer is (b) Ba.

Answer 2

Ba

Step-by-step explanation:

Let us consider the electrode potential of one of the options listed in the question,

Ba2+(aq) + 2 e- -----> Ba(s). -2.90V

It is very important to recall that a metal can only displace another metal from aqueous solution if that metal has a more negative reduction potential that the metal it displaced. This implies that if there are two metals A and B, A can only displace B from an aqueous solution of B if A has a more negative reduction potential than B.

The reduction potential of Mg^2+ is -2.37V. This is less negative than that of Ba^2+ which is -2.90V. Hence barium can reduce Mg^2+ to metallic Mg.