Why is CH3I have a higher boiling point than CH3Cl?
I thought, since Cl is more electronegative, it withdraws more electron density to its part and hence increase dipole movement within the atom and hence, requiring more energy to split them up and that implies higher boiling point for CH3Cl.
Boiling points depend more upon the INTERmolecular forces than they do on INTRAmolecular forces. Boiling points depend upon both the forces between molecules AND the molar mass of the compound. You are correct that the CH3Cl bond should be stronger than the CH3I bond but the boiling point of CH3I is higher because the molar mass of CH3I is higher.
As ch3i has greater surface area and also it has greater molar mass so it has more van der waal forces of attraction
Which results in increase in energy and thus it's b. Point is higher
Ah, boiling points, the great battle of the elements! While what you mentioned about electronegativity and dipole movement is no joke, there's more to the story. In the case of CH3I, the presence of a larger iodine atom actually causes the molecule to experience stronger London dispersion forces. These forces are like a game of molecular twister, creating temporary dipoles due to unequal electron distribution. So while CH3Cl may have some electronegativity shenanigans, CH3I emerges victorious in the boiling point battle! It's all about those tricky van der Waals forces.
Your logic is partially correct, but there are other factors to consider when comparing the boiling points of different molecules.
The boiling point of a compound is influenced by several factors, including intermolecular forces and molecular size.
In the case of CH3I and CH3Cl, both compounds have dipole-dipole interactions due to the partial positive charge on the hydrogen atom and the partial negative charge on the halogen atom (I and Cl).
It is true that chlorine (Cl) is more electronegative than iodine (I). As a result, the electron density in the CH3Cl molecule is withdrawn more strongly towards chlorine, creating a larger dipole. This stronger dipole-dipole interaction in CH3Cl does increase its boiling point compared to CH3I.
However, there is another significant factor to consider - molecular size. Iodine is a much larger atom than chlorine. Larger molecules tend to have stronger London dispersion forces (also known as van der Waals forces), which are caused by temporary fluctuations of electron density. These forces can play a significant role in determining boiling points.
In the case of CH3I, the larger iodine atom allows for stronger London dispersion forces between neighboring molecules compared to CH3Cl. These additional forces contribute to the increased boiling point of CH3I.
In summary, while the stronger dipole-dipole interaction in CH3Cl could lead you to believe it has a higher boiling point, the larger molecular size of CH3I strengthens the London dispersion forces, ultimately resulting in CH3I having a higher boiling point than CH3Cl.
First, is that Cl is more electronegative than Br , so it dipole moment increases then it requires more energy to split. So it have a high boiling point.
Second, it depends on the molar mass. So greater is the molar mass , more energy is required , so more is boiling point.