Confusion on reaction of aqueous solutions

[eneres]

When Calcium react with Copper(II) Nitrate, the balanced equation is simply:

Ca(s) + Cu(NO3)2 (aq) --> Ca(NO3)2(aq) + Cu(s) [no gas produced]

 

 

Why is it that hydrogen gas is also produced in the same reaction:

Ca(s) + 2H2O(l) --> Ca(OH)2(aq) + H2(g)

 

 

What would then be the complete balanced equation for the reaction between Calcium and Copper(II) Nitrate when there are 2 different reactions occuring in one chemical reaction?

 

Hence how do I determine when the water in an aqueous solution will or will not have a reaction to produce a gas in all other chemical reactions? Do aqueous solutions have any specific reactions in chemical reactions?

[vedmecum]

for a reaction to occur there must be decease in free energy . if there are two or more reaction then the one with large decrease in free energy will occur at faster rate . as far as your problem is concerned both reaction is feasible but first one occur at faster rate . i think this might help you.

[hermanntrude]

If you havent covered free energy yet, you will if you do first year degree-level chemistry courses.