Ammonia reacts with diatomic oxygen to form nitric oxide and water vapor: 4nh3 + 5o2 → 4no + 6h2o when 40.0 g nh3 and 50.0 g o2 are allowed to react, which is the limiting reagent?

Convert the mass to moles:

40.0 grams of NH3 / 17.03 g/mol = 2.35 moles NH3
50.0 grams of O2 / 31.998 g/mol = 1.56 moles O2

Get the actual ratio:

NH3/O2 = 2.35 / 1.56 = 1.5

The theoretical ratio is 4 NH3 to 5 O2, that is:

(NH3/O2)theo = 4 / 5 = 0.8

The limiting reagent would be O2

They are reagents that determine how much of the product is formed from a reaction.

From the balanced equation of the reaction:

4NH3 + 5O2 → 4NO + 6H2O

The mole ratio of NH3 to O2 is 4:5.

mole of 40.0 g NH3 = 40/17

                                     = 2.35 mole

Mole of 50.0 g O2 = 50/32

                               = 1.56 moles

Thus, NH3 seems to be in excess, making O2 to be the limiting reagent.

More on limiting reagents can be found here: link

2fe + 3h2so4 -> fe2(so4)3 + 3h2

it is necessary to balance equations in order to get the proper amount of reactants as well as products in order not to make a miscalculation.

you cannot change the subscripts as that would change the substance itself. for instance, diatomic elements such as h2 only have the subscript two when a gas. another example would be so4, if you were to change the subscript, the element would no longer be sulfate.

we change the coefficients instead as that only changes the number of molecules rather than the substance itself.

hope this !

1. they vary with a higher number because boiling is way hotter than melting