Question #77d3f
1 Answer
Explanation:
The interesting thing about this problem is that you don't really need to know the compound's molecular formula, but you do need to know its empirical formula.
As you know, a compound's empirical formula tells you the smallest whole number ratio that exists between the elements that make up said compound.
In this case, if the molecular formula is said to
So, your compound contains two moles of oxygen for every one mole of
Now, a
#m_"compound" = m_"M" + m_"O"#
#m_"O" = "18.00 g" - "10 g" = "8 g oxygen"#
At this point, all you really need to know if how many moles of oxygen you have in the sample. Use oxygen's molar mass to help you with that
#8 color(red)(cancel(color(black)("g"))) * "1 mole O"/(16.0 color(red)(cancel(color(black)("g")))) = "0.5 moles O"#
This means that sample must contain
#0.5 color(red)(cancel(color(black)("moles O"))) * "1 mole M"/(2color(red)(cancel(color(black)("moles O")))) = "0.25 moles M"#
Finally, to get the molar mass of element
#M_M = "10 g"/"0.25 moles" = color(green)("40 g mol"^(-1))#