Atoms of which element react spontaneously with mg2+(aq)? (1)chromium (2)barium (3)iron (4)zinc

Answer is: (2) barium.

Chemical reaction: Mg²⁺(aq) + Ba(s) → Mg(s) + Ba²⁺(aq).

Reactivity series is an empirical progression of a series of metals, arranged by their reactivity from highest to lowest (alkaline metals have highest reactivity and Noble metals lowest reactivity). 

This series are used to summarize information about the reactions of metals with acids or water, double displacement reactions (more reactive metals displace metals with lower reactivity) and the extraction of metals from their ores.

In this example, barium is more reactive than magnesium, iron, chromium and zinc are less reactive.

The complete answer contains the answer choices.


This is the complete question:


Atoms of which element react spontaneously with Mg2+(aq)? (1)chromium
(2)barium
(3)iron
(4)zinc


option 2. barium.

Explanation.

1) Mg ²⁺ (aq) is the aquous cation of the metal Mg.

2) Only a metal more reactive than Mg will be able to exchange with it the oxidation states.

3) Mg is an earth alkalyne metal (group 2 of the periodic table). The metals from this group are more reactive than the metals in the groups to its right: 3, 4, 5, 6, 7, ... Only the alkalyne metals (those in group 1) are more reactive than the earth alkalyne metals.

4) Of the list, barium is the only alkalyne metal, so it is more reactive than Mg and will be able to deliver 2 electrons to transform the cations Mg²⁺ into Mg while the very Ba will become Ba²⁺.

5) Chromium, iron and zinc are transition metals, so less metallic (reactive) than Mg.

The reaction will shift to the right