Percent composition is calculated as?

Percent composition is calculated as?

• A. Mass element/mass compound x 100
• B. Mass compound / mass element x 100
• C. Elemental composition is determined by molar mass
• D. Mass element / total mass x 100

Answer: (A)

Percent composition by mass is the fraction of a compound’s total mass that comes from a specific element, expressed as a percent. To find it, use the mass of that element in one amount of the compound divided by the total mass of that amount of compound, times 100. When you consider one mole of the pure compound, the numerator is the mass of the element in that mole and the denominator is the molar mass (the total mass) of the compound. This is why the correct form is mass of the element divided by mass of the compound, multiplied by 100. For example, in water the mass of H in one mole is 2.016 g and the molar mass is 18.015 g, so H percent = 2.016/18.015 × 100 ≈ 11.2%; O percent ≈ 88.8%. The other statements either invert the fraction or refer to a different idea, so they don’t give the correct calculation for percent composition.

Percent composition by mass is the fraction of a compound’s total mass that comes from a specific element, expressed as a percent. To find it, use the mass of that element in one amount of the compound divided by the total mass of that amount of compound, times 100. When you consider one mole of the pure compound, the numerator is the mass of the element in that mole and the denominator is the molar mass (the total mass) of the compound. This is why the correct form is mass of the element divided by mass of the compound, multiplied by 100. For example, in water the mass of H in one mole is 2.016 g and the molar mass is 18.015 g, so H percent = 2.016/18.015 × 100 ≈ 11.2%; O percent ≈ 88.8%. The other statements either invert the fraction or refer to a different idea, so they don’t give the correct calculation for percent composition.