In the explosion of a hydrogen-filled balloon, 0.40 g of hydrogen reacted with 3.2 g of oxygen. how many grams of water vapor are formed? (water vapor is the only product.) express your answer using two significant figures.

              3.568 g of H₂O

Solution:

The Balance Chemical Equation is as follow,

                                   2 H₂  +  O₂     →      2 H₂O

Step 1: Calculate the Limiting Reagent,

According to Balance equation,

               4.04 g (2 mol) H₂ reacts with  =  32 g (1 mol) of O₂

So,

                   0.40 g of H₂ will react with  =  X g of O₂

Solving for X,

                       X  =  (0.40 g × 32 g) ÷ 4.04 g

                       X  =  3.17 g of O₂

It means 0.4 g of H₂ requires 3.17 g of O₂, while we are provided with 3.2 g of O₂ which is in excess. Therefore, H₂ is the limiting reagent and will control the yield of products.

Step 2: Calculate amount of Water produced,

According to equation,

                4.04 g (2 mol) of H₂ produces  =  36.04 g (2 mol) of H₂O

So,

                        0.40 g of H₂ will produce  =  X moles of H₂O

Solving for X,

                      X  =  (0.40 g × 36.04 mol) ÷ 4.04 g

                      X  =  3.568 g of H₂O