1. Define “molarity” and calculate it for 0.5 moles of NaCl dissolved in 2L of solution.
Molarity = moles of solute / liters of solution. 0.5 mol / 2L = 0.25 M.
2. Balance this equation:
Fe+O2→Fe2O3Fe+O2→Fe2O3
4Fe + 3O₂ → 2Fe₂O₃.
3. What is the pH of a solution with [H ] = 1x10 ³ M? Is it acidic or basic?⁺ ⁻
pH = -log(1x10 ³) = 3. Acidic (pH < 7).⁻
4. Explain the difference between exothermic and endothermic reactions.
Exothermic releases heat (feels hot), endothermic absorbs heat (feels cold).
5. Name the type of bond in H₂O and describe its polarity.
Covalent bond. Polar because oxygen is more electronegative, pulling electrons closer.
6. Convert 25°C to Kelvin.
25 + 273.15 = 298.15 K.
7. What is Avogadro’s number?
6.022x10²³ particles per mole.
8. Write the electron configuration for sulfur (atomic number 16).
1s² 2s² 2p⁶ 3s² 3p⁴.
9. Identify the oxidation state of nitrogen in NO₃ .⁻
+5. (O is -2 each: 3(-2) = -6. Overall charge -1 = N + (-6) → N = +5).
10. What happens to pressure if volume decreases (at constant temperature)?
Pressure increases (Boyle’s Law: P₁V₁ = P₂V₂).
11. Define “limiting reactant” in a chemical reaction.
The reactant that runs out first, stopping the reaction and determining max product.
