Percentage of Magnesium by mass

= (mass of magnesium)/(mass of ocean water)`xx100%`

`= 1.3/1000xx100%`

`= 0.13%`

*So the percentage mass of Magnesium in ocean water is 0.13%.*

Percentage of Magnesium by mass

= (mass of magnesium)/(mass of ocean water)`xx100%`

`= 1.3/1000xx100%`

`= 0.13%`

*So the percentage mass of Magnesium in ocean water is 0.13%.*