CIE iGCSE Co-Ordinated Science C2.6 Giant covalent structures Exam Style Questions Paper 2
Question
Which statements describe the structure of silicon(IV) oxide?
1. Each oxygen atom is attached to two silicon atoms.
2. Each oxygen atom is attached to four silicon atoms.
3. Each silicon atom is attached to two oxygen atoms.
4. Each silicon atom is attached to four oxygen atoms.
(A) 1 and 3 (B) 1 and 4 (C) 2 and 3 (D) 2 and 4
▶️Answer/Explanation
Ans : B
Question
Which statements explain why graphite conducts electricity and why it can act as a lubricant?
- It is a macromolecule.
- It has mobile electrons.
- It has strong covalent bonds.
- It has weak forces between its layers.
A) 1 and 3
B) 1 and 4
C) 2 and 3
D) 2 and 4
▶️Answer/Explanation
Answer: D) 2 and 4
Explanation: Graphite conducts electricity due to the presence of mobile electrons within its layers. It acts as a lubricant because the weak forces between its layers allow them to slide over each other easily.
Question
Which statements explain why graphite conducts electricity and acts as a lubricant?
1 It has many strong covalent bonds.
2 It has mobile electrons.
3 It has weak forces between sheets of carbon atoms.
4 It is a macromolecule.
A 1 and 2
B 1 and 4
C 2 and 3
D 3 and 4
▶️Answer/Explanation
Answer: C
Explanation: Graphite conducts electricity because it has delocalized electrons that are free to move (statement 2). It acts as a lubricant because the weak forces between its layers of carbon atoms allow the layers to slide over each other easily (statement 3).
Question
Silicon(IV) oxide has a giant molecular structure. Which row is correct?
| number of oxygen atoms bonded to each silicon atom | number of silicon atoms bonded to each oxygen atom | |
|---|---|---|
| A | 2 | 2 |
| B | 2 | 4 |
| C | 4 | 2 |
| D | 4 | 4 |
▶️Answer/Explanation
Answer: C
Explanation: In SiO₂, each Si atom forms 4 covalent bonds with O atoms (tetrahedral arrangement), while each O atom bridges between 2 Si atoms.