Question

Given the equation `2H_2O ->2H_2 + O_2`, how many moles of `H_2O` would be required to produce 2.5 moles of `O_2`?

Answer 1

`5` moles of `H_2O`

Explanation:

Since the chemical equation,

`color(red)2H_2O->2H_2+color(blue)1O_2`

requires a specific number of moles of the reactant, then a specific number of moles of the products are created.

With this knowledge, you can create a mole ratio.

The general format of a mole ratio is as follows:

`color(blue)(|bar(ul(color(white)(a/a)color(black)(("required based on balanced equation")/("product based on balanced equation")=("required")/("product"))color(white)(a/a)|)))`

In your case, you're looking for the moles of `H_2O` required to make `2.5` moles of `O_2`.

Thus, your mole ratio would be:

`(color(red)2color(white)(i)molcolor(white)(i)H_2O)/(color(blue)1color(white)(i)molcolor(white)(i)O_2)=x/(2.5color(white)(i)molcolor(white)(i)O_2)`

`color(darkorange)(rArr)`where `x` represents the moles of `H_2O` required

From this point on, your goal is to solve for `x` to find the moles of `H_2O` required to produce `2.5` moles of `O_2`.

`x=2.5color(purple)cancelcolor(black)(molcolor(white)(i)O_2)xx(2color(white)(i)molcolor(white)(i)H_2O)/(1color(purple)cancelcolor(black)(molcolor(white)(i)O_2))`

`x=color(green)(|bar(ul(color(white)(a/a)5color(white)(i)molcolor(white)(i)H_2Ocolor(white)(a/a)|)))`