Explanation

• Lewis Waterman invented the first practical fountain pen in 1884.
• He was an American inventor who improved the ink-feeding system.
• His design regulated ink flow and reduced leakage.
• The fountain pen stores ink in a reservoir and delivers it to the nib.

Last verified on 29-10-2026

Explanation

• Paschen, Brackett, Pfund, Humphreys = Infrared

Additional information:

• Lyman series = Ultraviolet
• Balmer series = Visible

Last verified on 29-10-2026

Explanation

Formula: En = -1312 / n^2 kJ/mole

For n=2: E2 = -1312 / 4 = -328.25 kJ/mole

Last verified on 29-10-2026

Explanation

Formula: Bond order = (Nb - Na) / 2

For O2:

Total electrons = 16

Configuration: σ1s² σ_1s² σ2s² σ_2s² σ2pz² π2px² π2py² π_2px¹ π_2py¹

Bonding electrons (Nb) = 10

Antibonding electrons (Na) = 6

Bond order = (10 - 6) / 2 = 4/2 = 2

Means O=O double bond, which also explains its 2 unpaired electrons (paramagnetic).

Last verified on 29-10-2026

Explanation

• Degenerate orbitals are orbitals that have the same energy.
• The three p orbitals (px, py, pz) in an isolated atom have the same energy.
• They have different directions but equal energy.

Last verified on 29-10-2026

Explanation

1. 1st line (H-alpha) = electron from n=3 to n=2 : n1=2, n2=3
2. 2nd line (H-beta) = electron from n=4 to n=2 : n1=2, n2=4
3. 3rd line (H-gamma) = electron from n=5 to n=2 : n1=2, n2=5

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