Metal ore has other elements in it as well. Also sediment and stone might cover the ore. We don't want to have a phone with sediment on it do we? thus these few reasons are why.
Answer : The volume of
produced will be, 0.8 liters.
Explanation : Given,
Volume of
= 1.2 L
At STP, 1 mole of substance contains 22.4 L volume of substance.
The given balanced chemical reaction is:

From the balanced chemical reaction we conclude that,
As,
volume of
produced
volume of 
So,
volume of
produced
volume of 
Therefore, the volume of
produced will be, 0.8 liters.
The hydrogen bond is a comparatively weak interaction between a proton hop and an electronegative atom present in a molecule. The hydrogen bond plays a very important role for the determination of state of a compound like gaseous, liquid or solid. The strength of the hydrogen bond depends on the close distance between the participants i.e. the electronegative atom and proton hop. There remains strong hydrogen bond between the two water molecules which is expressed as O....H. The distance of the hydrogen bond is 1.8A° formed between each proton hops of two neighboring water molecules. The hydrogen bond interaction is shown in the figure.