Anthony T. answered • 06/15/21

Patient Math & Science Tutor

Start with a balanced equation which you already have.

**4NH3 + 5O2 = 4NO + 6H2O**

Now ask yourself, "what do I want to find". You want to know how many moles of NO are produced.

What are you given? You are given that you start with 6.96 g NH3 and excess O2.

Now you need the correct conversion factor. The conversion factor is a fraction with the numerator containing the quantity you are trying to find, and the denominator containing what you are given.

4 moles NO / 4 x mol mass of NH3 Note that the numerator is in moles of NO which is the coefficient of NO in the balanced equation. The denominator includes the coefficient for NH3 x mol. mass of NH3. It should be this way whenever a substance is given in grams. Putting numbers in the factor gives you

4 moles NO / 4 x 17.031 g /mole = 0.0587 moles NO per gram of NH3. Now multiply the factor result by the number of grams NH3 you were given.

0.0587 moles NO / g NH3 x 6.96 g NH3 = 0.409 g NO produced.

This is probably not how it is taught, but I find it more straightforward.

Anthony T.

This was they way I was taught years ago. The modern approach emphasizes gram to mole, mole to gram, and mole to mole conversions. If you compare the two approaches, they are really the same thing except what I showed you does it in fewer steps.06/15/21

Kitty C.

Thanks for your help so much! This way definitely gets the answer easier than I was previously taught!06/15/21