And if you go to the shop with #£50-00#, make a purchase for #£12-99#, would you have cause for complaint if you received #£27-01# in change? And these days you don't even get the change, you must check your receipt to make sure that the DEBIT made on your account is EQUAL to the CREDIT made to the shop's account....well, you must do this if you want to avoid spending hours on a call queue trying to get your card sorted.
And so look at the mass balance of your equation....
#underbrace(H_2+O_2)_"34 g"rarrunderbrace(H_2O)_"18 g"#
Stoichiometry has NOT BEEN observed; whereas mass and charge are balanced in every chemical reaction EVER observed...
On the other hand is stoichiometry observed for...
#underbrace(H_2+1/2O_2)_"18 g"rarrunderbrace(H_2O)_"18 g"#
...or for...
#underbrace(2H_2 +O_2)_"36 g" rarr underbrace(2H_2O)_"36 g"#...…..
