Question

For the theoretically perfect reaction 2H2 + O2 -----> 2H2O, if you react 300 molecules of hydrogen and 200 molecules of oxygen, how many oxygen molecules will you have that do not engage in the reaction?

Answer 1

Answer : The number of oxygen molecules that do not engage in the reaction are 50 molecules.

Explanation :

The balanced chemical reaction is,

`2H_2+O_2\rightarrow 2H_2O`

From the balanced chemical reaction we conclude that,

As, 2 molecules of hydrogen react with 1 molecule of oxygen

So, 300 molecules of hydrogen react with
`(300)/(2)=150` molecules of oxygen

The number of oxygen molecules reacted = 150 molecules

Now we have to determine the number of oxygen molecules that do not engage in the reaction.

Number of oxygen molecules left = Given number of oxygen molecules - Number of oxygen molecules reacted

Number of oxygen molecules left = 200 - 150

Number of oxygen molecules left = 50 molecules

Therefore, the number of oxygen molecules that do not engage in the reaction are 50 molecules.

Answer 2

From the given balanced chemical reaction, every 2 moles of hydrogen will need a mole of oxygen to form water. Thus, 300 moles of hydrogen will require only 150 moles of O2. Since there are 200 moles of oxygen, 50 of which will not be engage in the reaction.