Solve this chemistry questions

Mass of Carbon (C) = 75 g
Mass of Hydrogen (H) = 25 g

Molar mass of C = 12 g/mol
Molar mass of H = 1 g/mol

Smallest number of moles = 6.25 mol

The empirical formula is $\boxed{\text{CH}_4}$.

Question Two (2)

a)
An empirical formula represents the simplest whole-number ratio of atoms of each element present in a compound. It shows the relative number of atoms, but not necessarily the actual number of atoms in a molecule.

b)
i- Four examples of non-metallic radicals are:

• Sulfate ($\text{SO}_4^{2-}$)
• Nitrate ($\text{NO}_3^{-}$)
• Carbonate ($\text{CO}_3^{2-}$)
• Phosphate ($\text{PO}_4^{3-}$)

ii- Two natural phenomena that support the kinetic theory of gas are:

• Diffusion: The spontaneous mixing of gases due to the random motion of their particles.
• Brownian motion: The random movement of microscopic particles suspended in a fluid (liquid or gas), resulting from their collision with the fast-moving atoms or molecules in the fluid.

Question Three (3)

a)
Degenerate orbitals are atomic orbitals that have the same energy level within a subshell. For example, the three p orbitals ($p_x, p_y, p_z$) in a given principal energy level are degenerate.

b)
i- Electronic configuration:
a- Scandium (Sc, atomic number 21): $\boxed{1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1}$ or $\boxed{[\text{Ar}] 4s^2 3d^1}$
b- Nickel (Ni, atomic number 28): $\boxed{1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^8}$ or $\boxed{[\text{Ar}] 4s^2 3d^8}$

ii- Two physical properties of water are:

• It is a colorless, odorless, and tasteless liquid at room temperature.
• It has a relatively high boiling point ($100^\circ\text{C}$ at standard pressure) and freezing point ($0^\circ\text{C}$ at standard pressure).

Question Four (4)

a)

$\text{pOH} = 12.0$

b)
i- Sodium chloride ($\text{NaCl}$) is formed through electrovalent bonding (ionic bonding) by the transfer of electrons between a sodium atom and a chlorine atom. A sodium atom (Na) has one valence electron, which it readily loses to achieve a stable octet, forming a positively charged sodium ion ($\text{Na}^+$). A chlorine atom (Cl) has seven valence electrons and readily gains one electron to achieve a stable octet, forming a negatively charged chloride ion ($\text{Cl}^-$). The oppositely charged ions ($\text{Na}^+$ and $\text{Cl}^-$) are then held together by strong electrostatic forces of attraction, forming the ionic compound sodium chloride.

ii- Two properties of electrovalent (ionic) compounds are:

• They typically have high melting and boiling points due to the strong electrostatic forces between ions.
• They are generally soluble in polar solvents like water and can conduct electricity when molten or dissolved in water.

Question Five (5)

a)
i- The solubility of a salt refers to the maximum amount of that salt (solute) that can dissolve in a given amount of solvent at a specific temperature to form a saturated solution.

ii- Two examples of insoluble salts are:

• Silver chloride ($\text{AgCl}$)
• Barium sulfate ($\text{BaSO}_4$)

b)

Molar mass of K = 39 g/mol
Molar mass of N = 14 g/mol
Molar mass of O = 16 g/mol

The solubility of $\text{KNO}_3$ is approximately $\boxed{10.1 \text{ moldm}^{-3}}$.