Question

what is the mathematical formula for computing mass percent composition from a chemical formula?
○ mass % of element x = \\(\frac{\text{mass of x in one mole of compound}}{\text{mass of one mole of the compound}}\\)
○ mass % of element x = \\(\frac{\text{mass of x in one mole of compound}}{\text{mass of one mole of the compound}} \times 100\\%\\)
○ mass % of element x = \\(\frac{\text{mass of one mole of the compound - mass of x in one mole of compound}}{\text{mass of one mole of the compound}} \times 100\\%\\)
○ mass % of element x = \\(\frac{\text{mass of x in one mole of compound}}{\text{mass of one mole of the compound}} \times 100\\%\\)

Explanation:

The formula for mass percent composition of an element \( X \) in a compound is calculated by taking the mass of \( X \) in one mole of the compound, dividing it by the mass of one mole of the compound, and then multiplying by \( 100\% \). Let's analyze each option:

• First option: \( \text{mass \% of element } X=\frac{\text{mass of } X \text{ in one mole of compound}}{\text{mass of one mole of the compound}}\times 100\% \) which matches the correct formula.
• Second option: The numerator and denominator are reversed in the fraction part before multiplication, so it's incorrect.
• Third option: The fraction is \( \frac{\text{mass of } X \text{ in one mole of compound}}{\text{mass of one mole of the compound}} \) but the multiplication by \( 100\% \) is misrepresented (extra fraction), so incorrect.
• Fourth option: The fraction is \( \frac{\text{mass of } X \text{ in one mole of compound}}{\text{mass of one mole of the compound}} \) but the structure is incorrect as it has a wrong fraction setup.

Answer:

The first option: \( \text{mass \% of element } X=\frac{\text{mass of } X \text{ in one mole of compound}}{\text{mass of one mole of the compound}}\times 100\% \)