If you burn 48.6 g of hydrogen and produce 434 g of water, how much oxygen reacted?

            385.69 g of O₂

Solution:

The Balance Chemical equation for said reaction is as follow;

                                       2 H₂  +  O₂    →   2 H₂O

According to Equation,

        4.032 g ( 2 mol) H₂ reacts to produce  =  36.03 g (2 mol) of H₂O

So,

        48.6 g H₂ on reaction will produce  =  X g of H₂O

Solving for X,

                     X =  (48.6 g × 36.03 g) ÷ 4.032 g

                     X  =  434.29 g of H₂O

It means that the H₂ provided is in Excess. Therefore, the yield of product (H₂O) is being controlled by O₂ (Limiting Reagent).

So, According to Equation,

                    36.03 g (2 mol) H₂O is produced by  =  31.998 g (1 mol) of O₂

So,

                434.29 g of H₂O will be produced by  =  X g of O₂

Solving for X,

                     X =  (434.29 g × 31.998 g) ÷ 36.03 g

                    X  =  385.69 g of O₂

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