Question

Which of the following reactant pairs will not react together to produce a reaction? a Na + BaO b K + ZnBr2 c Al + HCl d Mg + H2O

Answer 1

According to your question, The pair which will not react is that of Mg + H2O. This is because magnesium cannot displace hydrogen gas from the water molecule. This reaction may only take place provided the water is in vapor form. This is to say that this reaction is only possible with water vapor to produce hydrogen gas.

So for you to determine the feasibility of a reaction all you need to put in mind is the reactivity series of various metals. For instance, potassium is above zinc in the reactivity series hence potassium will displace bromine from a solution of Zinc bromide.

Answer 2

$\bold{\mathrm{Mg}+\mathrm{H}_{2} \mathrm{O}}$ will not react together to produce a reaction.

Option: (d)

Explanation:  

• If we consider the reactivity of the different metal, high reactive metal can displace a lower reactive metal from its salt solution.  

• Sodium is more reactive as compared to Ba. Also Potassium is more reactive as compared to zinc. And Aluminium is more reactive then hydrogen.  

• However magnesium does not react with water in liquid state to liberate hydrogen gas.  

• It can react with water only if water is present in vapour state. So the correct answer will be magnesium and water.