1. what is the Lewis structure for CH3Cl and what is its molecular shape?
2. What is the observation on adding a solute crystal to a supersaturated solution?
a) It becomes a colloidal solution
b) The solute dissolves in the solution
c) The solution desaturates
d) The solute precipitates out of the solution
The correct answer and explanation is:
1. Lewis Structure and Molecular Shape of CH₃Cl
The Lewis structure of CH₃Cl (methyl chloride) consists of:
- A carbon (C) atom at the center, forming four single bonds.
- Three hydrogen (H) atoms each forming a single bond with carbon.
- One chlorine (Cl) atom forming a single bond with carbon.
- Chlorine has three lone pairs of electrons.
The molecular shape of CH₃Cl is tetrahedral, based on the VSEPR (Valence Shell Electron Pair Repulsion) theory. Since carbon has four regions of electron density around it (three H atoms and one Cl atom), these regions arrange themselves to minimize repulsion, resulting in a tetrahedral shape with bond angles of approximately 109.5°.
2. Observation on Adding a Solute Crystal to a Supersaturated Solution
Correct Answer: d) The solute precipitates out of the solution.
Explanation (300 words)
A supersaturated solution is an unstable solution that contains more dissolved solute than it can normally hold at a given temperature. This state occurs when a solution is carefully prepared by dissolving excess solute at a higher temperature and then cooling it slowly without disturbance.
When a solute crystal is added to a supersaturated solution, it acts as a nucleation site. This disturbs the delicate equilibrium and causes the excess solute to rapidly precipitate out of the solution in a crystalline form. This happens because the solution was already holding more solute than its saturation limit, so the system moves toward a more stable, saturated state by releasing the extra solute as a solid.
For example, if a supersaturated sodium acetate solution is prepared and a tiny crystal of sodium acetate is introduced, a sudden and rapid crystallization occurs. This is often used in hot packs, where a small metal disk initiates crystallization, releasing heat.
This principle is widely used in:
- Industrial Crystallization: Purification of compounds through controlled precipitation.
- Rock Candy Formation: Supersaturated sugar solutions crystallize upon the addition of a sugar crystal.
- Chemical Analysis: Supersaturation is used to precipitate specific compounds from solutions.
Thus, the correct observation when adding a solute crystal to a supersaturated solution is that the solute precipitates out as the solution returns to a saturated state.
Here is the image of the Lewis structure and molecular shape of CH₃Cl (methyl chloride). Let me know if you need any modifications or additional explanations!
