QUESTION 2 [14 marks]
Question 2.1 [2 marks]
Define the term covalent bond.
A covalent bond is a chemical bond formed when two atoms share one or more pairs of electrons, enabling each atom to attain the electron configuration of a noble gas and achieve greater stability.
Question 2.2 [3 marks]
Draw the Lewis diagram for CaF₂.
The Lewis diagram for calcium fluoride (CaF₂) can be represented as follows:
:F:
|
:Ca: --- :F:
In the Lewis structure:
- Calcium (Ca) is represented with no dots since it has 2 valence electrons, which it loses to become Ca²⁺.
- Each Fluorine (F) atom has three lone pairs of electrons and shares one pair (single bond) with calcium.
Question 2.3 [2 marks]
Which of the TWO products of this reaction would most likely be a crystalline solid at room temperature? Explain your answer.
Calcium sulfate (CaSO₄) and hydrogen fluoride (HF) are the two products. Calcium sulfate (CaSO₄) would most likely be a crystalline solid at room temperature. This is because CaSO₄ is an ionic compound formed from calcium ions and sulfate ions, which generally crystallize in a solid structure due to strong ionic bonds. In contrast, HF is a molecular compound with hydrogen bonds that can exist as a gas or liquid at room temperature.
Question 2.4 [2 marks]
Define electronegativity.
Electronegativity is the tendency of an atom in a molecule to attract shared electrons towards itself. It is measured on a scale (such as the Pauling scale), where higher values indicate a greater ability to attract electrons.
Question 2.5 [2 marks]
Use electronegativity to determine the type of bond that CaF₂ has.
Calcium (Ca) has an electronegativity value of about 1.0, while fluorine (F) has a value of about 4.0. The difference in electronegativity is 4.0 - 1.0 = 3.0, which indicates that the bond is ionic, as the difference is greater than 1.7. This means that calcium donates its electrons to fluorine, resulting in the formation of Ca²⁺ and F⁻ ions.
Question 2.6 [1 mark]
What is the VSEPR shape of HF?
The VSEPR shape of HF (hydrogen fluoride) is linear. This is because there are two atoms (H and F) involved, and there are no lone pairs on the central atom (F) to influence the shape.
Question 2.7 [2 marks]
Is HF a polar or non-polar molecule? Explain your answer.
HF is a polar molecule. This is due to the significant electronegativity difference between hydrogen (H) and fluorine (F). Fluorine is much more electronegative than hydrogen, causing the shared electrons to be drawn closer to the fluorine atom. This creates a partial negative charge (δ-) on the fluorine and a partial positive charge (δ+) on the hydrogen, resulting in a dipole moment and making HF polar.
QUESTION 3 [14 marks]
Question 3.1.1 [2 marks]
Define the term boiling point.
The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure surrounding the liquid, causing it to change into a gas. At this temperature, the liquid's molecules have sufficient energy to overcome intermolecular forces and enter the gaseous state.
Question 3.1.2 [1 mark]
Calculate the molecular mass of compound D.
To calculate the molecular mass of compound D, we would need the molecular formula of compound D. Without specific information provided, one cannot perform a calculation.
However, if you provide the molecular formula, I can help calculate the molecular mass.
Question 3.1.3 [1 mark]
In what phase is compound D at 100 °C?
The phase of compound D at 100 °C depends on its boiling point:
- If the boiling point is below 100 °C, it would be a gas.
- If the boiling point is at (or above) 100 °C, it would be a liquid (or solid if its boiling point is significantly high).
Again, this relies on the boiling point data provided in Table 1.
Question 3.1.4 [1 mark]
Name the main type of intermolecular force present in compound A.
The main type of intermolecular force present in compound A can vary depending on its molecular structure. Without specific details about the compound, it's challenging to identify the intermolecular forces.
If compound A is known to be, for example, a polar molecule, the main intermolecular forces could be dipole-dipole interactions, or if it is a nonpolar molecule, the main intermolecular forces could be London dispersion forces.
Please provide specific details about compound A for an accurate answer.
1 answer