Explanation

• KCl has formula mass.
• KCl is an ionic compound.
• It exists as a crystal lattice, not discrete molecules.
• So we use formula mass.

Additional information:

• NH₃, C₆H₁₂O₆, CO₂ are covalent molecules. 
• They exist as discrete molecules.
• So we use molecular mass.

Last verified on 29-10-2026

Explanation

Molar mass of water (H₂O) = 2(1) + 16 = 18 g/mol

Moles = Mass / Molar mass

Moles = 90 / 18 = 5 moles

Last verified on 29-10-2026

Explanation

Finally you have the correct numbers for 24g of CO₂

24g = 24/44 = 0.545 mol

1. 3.28 × 10²³ molecules -> CORRECT
2. 0.545 moles -> CORRECT
3. 17.45 g of oxygen -> CORRECT (32/44 x 24)
4. 22.4 dm³ at STP -> INCORRECT

22.4 dm³ is volume for 44g (1 mole). 

For 24g volume = 0.545 x 22.4 = 12.21 dm³

Last verified on 29-10-2026

Explanation

• Spectroscopy is the study of the interaction of light with matter, including the absorption and emission of light.
• It is used to identify elements and compounds by analyzing their characteristic spectra.

Additional information:

• Atomic spectroscopy is used to study the electronic structure of atoms.

Last verified on 29-10-2026

Explanation

• The n+l rule, also called the Madelung rule.
• It is used to determine the order in which atomic orbitals are filled according to their energy.
• Here, n is the principal quantum number and l is the azimuthal (angular momentum) quantum number.
• The orbital with the lower n+l value fills first.
• If two orbitals have the same n+l value, the orbital with the lower n value fills first.

Last verified on 29-10-2026