What is percentage composition in chemistry?

Expression of relative amounts of each element in a compound as percentage by mass.

Fill in the blank: Mass percentage formula is _____ ÷ total mass × 100.

Mass of component

True or False: Empirical formula shows the actual number of atoms in a molecule.

False. Empirical formula shows the simplest whole-number ratio of atoms.

Which represents simplest whole-number ratio of atoms?
A) Molecular formula
B) Empirical formula
C) Structural formula
D) Chemical formula

B) Empirical formula

What mathematical relationship connects molecular and empirical formulas?

Molecular formula = (Empirical formula) × n, where n is positive integer.

How do you calculate vapour density from molecular mass?

Vapour density = Molecular mass ÷ 2

In C₆H₁₂O₆, why does oxygen have higher mass percentage than carbon?

Oxygen has greater atomic mass (16.00) than carbon (12.01) despite same atom count.

A compound contains 40% C, 6.67% H, 53.33% O. What are moles if sample is 100g?

C: 3.33 mol, H: 6.67 mol, O: 3.33 mol

Fill in the blank: To find empirical formula, divide all mole values by _____.

Smallest mole value

True or False: Different compounds can have the same empirical formula.

True. C₆H₁₂O₆, CH₃COOH and HCHO all have empirical formula CH₂O.

If molecular mass is 180 and empirical mass is 60, what is n?

A) 1
B) 2
C) 3
D) 4

C) 3

What happens when empirical formula ratios are not whole numbers?

Multiply all ratios by appropriate integer to obtain whole numbers.

Why do we assume 100g sample in percentage composition calculations?

Percentage values directly become grams, simplifying mass-to-mole conversions.

A compound has C:H:O mass ratio 3:1:4. What is the empirical formula?

C₃H₁₂O₃ or simplest form CH₄O

True or False: Empirical and molecular formulas are always different.

False. Some compounds have identical empirical and molecular formulas.

Fill in the blank: Molecular mass = _____ × vapour density.

2

What is essential for empirical formula determination?

A) Mass percentage
B) Molar mass
C) Atomic mass
D) Formula mass

A) Mass percentage

If a compound's vapour density is 32, what is its molecular mass?

64 g/mol

What step follows converting mass to moles in empirical formula determination?

Divide all mole values by smallest mole value to get simplest ratio.

A compound has empirical formula CH₂ and molecular mass 84. What is molecular formula?

C₆H₁₂

True or False: In H₂O, hydrogen contributes about 11% of total mass.

True. Hydrogen mass percentage in water is approximately 11.21%.

Fill in the blank: Different compounds with same empirical formula are called _____.

Isomers or compounds with same empirical formula