Question

the______is defined as the percentage by mass of each element present in a the compound.
o mole percent
o molar ratio
o percent composition
o compound composition
question 2
1 pts
which of the following equations represents the percent composition of an element x present in a given mass of a compound?
o % x = \frac{\text{mass x}}{\text{mass compound}} × 100%
o % x = \frac{\text{mass x}}{\text{mass compound}}
o % x = \frac{\text{mass compound}}{\text{mass x}} × 100%
o % x = \frac{\text{mass compound}}{\text{mass x}}

Explanation:

• Question 1:
• Mole percent is related to the number of moles of a component in a mixture (not mass - based for a compound's elements).
• Molar ratio is about the ratio of moles of different substances (not mass - percentage of elements in a compound).
• Compound composition is a very general term. Percent composition specifically refers to the percentage by mass of each element in a compound.
• Question 2:
• The formula for percent composition of an element \(X\) in a compound is \(\%\text{X}=\frac{\text{mass X}}{\text{mass compound}}\times100\%\). The other options have incorrect numerator - denominator relationships. For example, \(\frac{\text{mass compound}}{\text{mass X}}\times100\%\) would give a value greater than \(100\%\) (if \(\text{mass compound}>\text{mass X}\), which is usually the case for a single element in a compound) and is not the formula for percent composition. The non - percentage options (\(\frac{\text{mass X}}{\text{mass compound}}\) and \(\frac{\text{mass compound}}{\text{mass X}}\)) lack the percentage conversion factor.

Answer:

• Question 1: percent composition
• Question 2: \(\%\text{X}=\frac{\text{mass X}}{\text{mass compound}}\times100\%\) (the first option in Question 2)