Which of these alkaline earth metal oxides has the greatest percent by mass oxygen?

Question

these are the options: Barium Oxide, beryllium Oxide, Calcuim Oxide, Magnesium Oxide, and Strontium Oxide.

I have no clue how to do this! Could you explain how you got the answer for clarification also? Thanks!

Answer 1

Formulas are as follows:

BaO, BeO, CaO, MgO, and SrO.

The formulas are obtained by combining a +2 metal ion with the -2 oxide ion.

Percent Oxygen by mass is calculated as follows:

(Mass of oxygen) divided by (formula mass) x 100%

The masses of the elements can be found on the periodic table:

O=16.0, Be=9.0, Mg=24.3, etc.

Since all formulas have exactly one oxygen, the formula that has the LARGEST  percent oxygen by mass will be the one that has the SMALLEST formula mass. This will be beryllium oxide, BeO.

%O = (16/25) = 64%

Compare that with MgO and you get (16/40.3) = 39.7%

All other oxides will have even smaller percentages of oxygen.

Answer 2

Beryllium oxide...the percent of oxygen is determined from the molecular weight of each minera, e.g BeO has 63.97% oxygen content.l  

Answer 3

Be is the lightest of the alkaline earth metals so definitely its oxide has greater percentage of oxygen (63.97%) than others