# Question #e888f

Jul 11, 2017

The number of oxygen atoms will be ${N}_{\textrm{A}} / 2$.

#### Explanation:

One definition of gram-equivalent is the mass of a substance that will combine with 1.008 g of hydrogen.

If we are talking about molecules of oxygen,

$\textcolor{w h i t e}{l l} 2 \text{H"_2color(white)(m) +color(white)(m) "O"_2color(white)(m) → 2"H"_2"O}$
$\text{4.032 g"color(white)(mm)"32.00 g}$

If we are talking about atoms of oxygen,

$\textcolor{w h i t e}{m} \text{H"_2 color(white)(m)+color(white)(m) "O"color(white)(m) → "H"_2"O}$
$\text{2.016 g"color(white)(ml)"16.00 g}$

In either case, 1.008 g of hydrogen combines with 8.000 g of oxygen.

One gram-equivalent of oxygen has a mass of 8.000 g.

$\text{Number of O atoms" = 8.000 color(red)(cancel(color(black)("g O"))) × (1 color(red)(cancel(color(black)("mol O"))))/(16.00 color(red)(cancel(color(black)("g O")))) × (N_text(A)color(white)(l) "O atoms")/(1 color(red)(cancel(color(black)("mol O")))) = N_text(A)/2color(white)(l) "O atoms}$.