EIT Chemistry and Materials Science 2 — Questions and Answers
Question 1: Which type of bond results from the sharing of electrons between two atoms?
- Covalent bond (Correct answer)
- Ionic bond
- Metallic bond
- Van der Waals bond
Correct answer: Covalent bond
Covalent bonds form when atoms share electron pairs, as in Hâ‚‚, Hâ‚‚O, and organic molecules.
Question 2: The yield strength of a material is defined as the stress at which:
- Significant permanent (plastic) deformation begins (Correct answer)
- The material fractures
- Elastic deformation begins
- The ultimate tensile strength is reached
Correct answer: Significant permanent (plastic) deformation begins
Yield strength marks the onset of plastic deformation — below this stress, deformation is elastic and recoverable.
Question 3: In an iron-carbon phase diagram, the eutectoid composition occurs at approximately:
- 0.76 wt% C at 727°C (Correct answer)
- 4.3 wt% C at 1147°C
- 2.14 wt% C at 1147°C
- 6.7 wt% C at 727°C
Correct answer: 0.76 wt% C at 727°C
The eutectoid point in the Fe-C system is 0.76 wt% C at 727°C, where austenite transforms to pearlite (ferrite + cementite).
Question 4: The rate of a chemical reaction generally __________ with increasing temperature.
- Increases exponentially (Arrhenius) (Correct answer)
- Decreases linearly
- Remains constant
- Decreases exponentially
Correct answer: Increases exponentially (Arrhenius)
Arrhenius equation k = Ae^(−Ea/RT) shows exponential increase in rate constant k with temperature T.
Question 5: Polymer glass transition temperature (Tg) is the temperature below which the polymer becomes:
- Rigid and glassy (brittle) (Correct answer)
- Rubbery and flexible
- Crystalline
- Liquid
Correct answer: Rigid and glassy (brittle)
Below Tg, chain mobility freezes and the polymer becomes stiff and brittle like glass; above Tg it is rubbery.
Question 6: Le Chatelier's principle states that if a stress is applied to a system at equilibrium, the system will:
- Shift to partially counteract the applied stress (Correct answer)
- Remain unchanged
- Always increase temperature
- Shift to amplify the applied stress
Correct answer: Shift to partially counteract the applied stress
Le Chatelier's principle predicts that equilibrium shifts in the direction that opposes the imposed change (stress).
EIT Chemistry and Materials Science 2
Which type of bond results from the sharing of electrons between two atoms?