Tahsili Chemistry

Question 1

What is the electron configuration of carbon (atomic number 6)?

Accepted Answer

1s² 2s² 2p²

Answer

Carbon has 6 electrons. Filling in order: 1s² (2 electrons), 2s² (2 electrons), 2p² (2 electrons). Total: 6 electrons. This configuration explains carbon's ability to form 4 covalent bonds.

Question 2

What type of bond forms between sodium (Na) and chlorine (Cl)?

Accepted Answer

Ionic bond

Answer

Sodium (metal, low electronegativity) transfers an electron to chlorine (non-metal, high electronegativity), forming Na⁺ and Cl⁻ ions. The electrostatic attraction between these oppositely charged ions is an ionic bond.

Question 3

What is the pH of a solution with a hydrogen ion concentration of 10⁻³ M?

Accepted Answer

3

Answer

pH = -log[H⁺] = -log(10⁻³) = -(-3) = 3. A pH of 3 is acidic (pH < 7). The pH scale measures acidity/basicity logarithmically.

Question 4

Balance the equation: __Fe + __O₂ → __Fe₂O₃

Accepted Answer

4Fe + 3O₂ → 2Fe₂O₃

Answer

Balanced: 4Fe + 3O₂ → 2Fe₂O₃. Check: Fe: 4 = 2×2 = 4 ✓. O: 3×2 = 6 = 2×3 = 6 ✓. Both sides have equal atoms of each element.

Question 5

What is Avogadro's number and what does it represent?

Accepted Answer

6.022 × 10²³ — the number of particles in one mole of a substance

Answer

Avogadro's number (6.022 × 10²³) is the number of atoms, molecules, or particles in one mole of any substance. It connects the atomic/molecular scale to the macroscopic scale, enabling conversion between mass and number of particles.

Tahsili Practice Test

Tahsili Practice Test

Tahsili Chemistry