What would be the empirical formula of a hypothetical compound that contains 60% by mass of element A (#A_(r1) = 10#) and 40% by mass of element B (#A_(r2) =20#)?
a. #"A"_3"B"_2#
b. #"AB"_3#
c. #"AB"_2#
d. #"A"_3"B"#
The answer is d. #"A"_3"B"# , why?
a.
b.
c.
d.
The answer is d.
1 Answer
Explanation:
Assuming that
A compound's percent concentration by mass essentially tells you how many grams of each element that makes up said compound you get per
In this case, your hypothetical compound contains two elements,
#"For A: " 60%#
#"For B: "40%#
So, what this tells you is that in
Now, in order to find the compound's empirical formula, you need to know the smallest whole number ratio that exists between its constituent elements.
Use the two molar masses to determine how many moles of each element are present in this
#"For A: " 60 color(red)(cancel(color(black)("g"))) * "1 mole A"/(10color(red)(cancel(color(black)("g")))) = "6 moles A"#
#"For B: " 40color(red)(cancel(color(black)("g"))) * "1 mole B"/(20color(red)(cancel(color(black)("g")))) = "2 moles B"#
To get the smallest whole number ratio, divide both values by the smallest one
#"For A: " (6color(red)(cancel(color(black)("moles"))))/(2color(red)(cancel(color(black)("moles")))) = 3#
#"For B: " (2color(red)(cancel(color(black)("moles"))))/(2color(red)(cancel(color(black)("moles")))) = 1#
This means that the empirical formula of the compound is
#"A"_3"B"_1 implies color(green)("A"_3"B")#