Question

What is the largest amount of H2O in grams that can be formed when 4.90 g of H2 reacts with 4.90 g of O2, based on the balanced reaction below.


2 H2 + O2 2 H2O

Answer 1

You should learn where the arrow keys are on your calculator and use them. --> or ==>
This is a limiting reagent problem and I work these the long way by solving two stoichiometry problems and taking the smaller value.
Convert 4.90 g H2 to moles. moles = grams/molar mass.
Convert4.90 moles O2 to moles the samw way.
Using the coefficients in the balanced equation, convert moles H2 to moles H2O.
With the same procedure, convert moles O2 to moles H2O.
You will obtain two answers; of course both can't be right. The correct answer in limiting reagent problems is ALWAYS the smaller value and the reagent producing that number is the limiting reagent.
Then grams H2O = moles H2O x molar mass H2O.