For the combustion of methane, CH4 + 2 O2 --> CO2 + 2 H2O, if the reaction starts with 4 moles oxygen (O2), how many moles of water (H2O) will be produced?

The correct name for n3-ion should be azide.

Your question is not clear but if you can explain yourself i would be glad to .  just trying to : ))

Hbr dissociates to form h+ and br-ca(oh)2 dissociates to form ca2+ and 2oh-the h+ and oh- react to form waterassuming the reactants are dissolved in water, the net reaction is h+ + oh- —> h2oif you’re asked to show all components of the reaction, the complete reaction is 2hbr + ca(oh)2 —> cabr2 + 2h2o