If 6.0X10^20 molecules of H2O are formed, how many molecules of O2 are reacted?

Question

Express to 2 sig figs. Express is proper scientific notation. You can not write superscripts so format you numbers as follows: 1.0E4 or 1.0X10^4.

Answer 1

Presumably, 1 molecule of O₂ will be able to produce 2 molecules of H₂O

6.0x10²⁰ molecules of H₂O x 1 molecule O₂/2 molecules H₂O = 3.0x10²⁰ molecules of O₂ needed.

Answer 2

Presumably, this refers to another question.  Remember, a stoichiometric problem can only be solved using a BALANCED CHEMICAL EQUATION.

 

Presumably this is a combustion, but, what is the reactant besides water?