Achemical reaction in which two or more substances undergo a chemical union to form a more complex substance is a reaction.

a. substitution
b. combination
c. decomposition
d. double replacement

Can someone me with 3 and 4 plz. this is for masteries test.

The sum of the oxidation numbers in a neutral compound is always

Butane gas reacts with oxygen gas to give carbon dioxide gas and water vapor (gas). if you mix butane and oxygen in the correct stoichiometric ratio, and if the total pressure of the mixture is 390 mmhg, what is the pressure (in mmhg) of water vapor after the reaction is completed (temperature and volume do not change).