In which compound is the percent by mass of oxygen greatest? A. BeO B. MgO C. CaO D. SrO

Question

asked Aug 1, 2016 13.8k views

2 Answers

Antonis Grigoriadis · Answer 1 · 2016-08-03T21:36:40+0000

The answer is A
Hide the Oxygen for a minute
Mass of elements:
Be:9.012
Mg:24.305
Ca:40.078
Sr:87.62
Out of all these choices, Be is the lightest

Mateus Brandao · Answer 2 · 2016-08-06T03:32:44+0000

Answer: BeO

Explanation:

percent by mass of oxygen
$=\frac{\text {mass of oxygen}}{\text {Total mass of substance}}* 100\%$

percent by mass of oxygen in BeO
$=(16g)/(25.01g/mol)* 100=63.97\%$

percent by mass of oxygen in MgO
$=(16g)/(40.30g/mol)* 100=39.70\%$

percent by mass of oxygen in CaO
$=(16g)/(56.08g/mol)* 100=28.53\%$

percent by mass of oxygen in SrO
$=(16g)/(103.62g/mol)* 100=15.44\%$