In the last blog post, we went through a common exam-based question on Chemical Bondings and revised briefly on:
- Types of Bondings
- Types of Structures & its properties
Today, we shall look at a few more exam-based Chemistry MCQ questions on this topic:
Which of the following is most likely to be the melting point of an ionic solid?
Ionic compounds tend to have high melting point and boiling point. They tend to exist as solids at room temperature and pressure.
Strong electrostatic forces of attraction holds the positive ions and the negative ions together in the giant ionic/crystal lattice structure.
As such, a large amount of energy is required to overcome these strong forces.
As such, answer in (Option D).
Which one of the following substances;
(i) is an element?
(ii) also forms crystals composed of small molecules?
C. Carbon dioxide
Option A: Copper is an element BUT it exists as positive metal ions surrounded by ‘sea of delocalised valence electrons’.
Option B: Graphite is an element BUT it exists as giant molecular structure of carbon atoms held together by strong covalent bonds.
Option C: Carbon dioxide exists as simple molecular structure (i.e. small molecules) BUT it is a compound.
Option D: Iodine is an element and it exists as a diatomic molecule (i.e. simple molecular structure). At room temperature, iodine is a solid so that diatomic molecules are packed very closely together in a regular pattern, to form “crystals”. DO NOT be tricked to think that iodine is an ionic compound due to the word “crystals” which is usually associated with ionic compound. It could also mean that simple molecular structures are packed closely together in a regular pattern when they are in solid state. You can refer to Kinetic Particle Theory to learn more on 3 states of matter.
As such, answer is (Option D).
PS: Hmm, just realised this is quite a tricky question. Going to test my students in our O-Level Pure Chemistry Tuition Classes on the same question and see how they fare for it
I am sure you have learned something useful today.
Feel free to share it with your friends who need help in Basic Chemistry.