EIT Chemistry and Materials Science 1 — Questions and Answers
Question 1: The atomic number of an element represents the number of:
- Protons in the nucleus (Correct answer)
- Neutrons in the nucleus
- Electrons in the outermost shell
- Nucleons (protons + neutrons)
Correct answer: Protons in the nucleus
The atomic number Z uniquely identifies an element and equals the number of protons in the nucleus.
Question 2: Avogadro's number (6.022 × 10²³) represents the number of entities in:
- One mole of a substance (Correct answer)
- One gram of any element
- One liter of gas at STP
- One kilogram of any compound
Correct answer: One mole of a substance
One mole of any substance contains exactly 6.022 × 10²³ particles (atoms, molecules, ions, etc.).
Question 3: The pH of a neutral aqueous solution at 25°C is:
- 7 (Correct answer)
- 0
- 14
- 1
Correct answer: 7
At 25°C, pure water has [H⁺] = [OH⁻] = 10⁻⁷ mol/L, giving pH = −log(10⁻⁷) = 7.
Question 4: The ideal gas law PV = nRT uses R = 8.314 J/(mol·K) when pressure is in:
- Pascals (Pa) (Correct answer)
- Atmospheres (atm)
- Bar
- mmHg
Correct answer: Pascals (Pa)
R = 8.314 J/(mol·K) = 8.314 Pa·m³/(mol·K), consistent with SI units where P is in Pascals and V in m³.
Question 5: The crystal structure of iron (Fe) at room temperature is:
- Body-centered cubic (BCC) (Correct answer)
- Face-centered cubic (FCC)
- Hexagonal close-packed (HCP)
- Simple cubic (SC)
Correct answer: Body-centered cubic (BCC)
Iron is BCC at room temperature (α-iron), transforming to FCC (γ-iron) above 912°C.
Question 6: Faraday's law of electrolysis states that the mass deposited at an electrode is proportional to:
- The total charge passed through the electrolyte (Correct answer)
- The voltage applied
- The electrode surface area
- The temperature of the solution
Correct answer: The total charge passed through the electrolyte
Faraday's law: m = MIt/(nF), where mass deposited is directly proportional to total charge Q = It passed.
EIT Chemistry and Materials Science 1
The atomic number of an element represents the number of: