the melting point of NaCl is very high but ethanol is a volatile substance by the cause behind this
Answers
THIS IS THE REASON
When a solute is added to a solvent, the vapor pressure of the solvent (above the resulting solution) is less than the vapor pressure above the pure solvent. The boiling point of a solution, then, will be greater than the boiling point of the pure solvent because the solution (which has a lower vapor pressure) will need to be heated to a higher temperature in order for the vapor pressure to become equal to the external pressure (i.e., the boiling point).
The boiling point of the solvent above a solution changes as the concentration of the solute in the solution changes (but it does not depend on the identity of either the solvent or the solute(s) particles (kind, size or charge) in the solution).
Non-Volatile Solutes
The boiling point of the solvent above a solution will be greater than the boiling point of the pure solvent whether the solution contains a non-volatile solute or a volatile solute. However, for simplicity, only non-volatile solutes will be considered here.
Experimentally, we know that the change in boiling point of the solvent above a solution from that of the pure solvent is directly proportional to the molal concentration of the solute:
T = Kbm
where:
T is the change in boiling point of the solvent,
Kb is the molal boiling point elevation constant, and
m is the molal concentration of the solute in the solution.
Note that the molal boiling point elevation constant, Kb, has a specific value depending on the identity of the solvent.
solvent normal boiling point, oC Kb, oC m-1
water 100.0 0.512
acetic acid 118.1 3.07
benzene 80.1 2.53
chloroform 61.3 3.63
nitrobenzene 210.9 5.24
The following graph shows the normal boiling point for water (solvent) as a function of molality in several solutions containing sucrose (a non-volatile solute). Note that the normal boiling point of water increases as the concentration of sucrose increases.
The figure below shows a microscopic view of the surface of pure water. Note the interface between liquid water (below) and water vapor (above).
Non-Volatile Solutes
The figures below illustrate how the vapor pressure of water is affected by the addition of the non-volatile solute, NaCl.
Note that:
there are fewer water molecules in the vapor (i.e., lower vapor pressure) above the NaCl solution than in the vapor above pure water, and
the boiling point of the NaCl solution will be greater than the boiling point of pure water.
Microscopic view of the surface of liquid water the surface of an aqueous NaCl solution
.
NOrmal boiling point = 100.0oC. 1.0 M NaCl solution
Normal boiling point = 101.0oC.
Note that the ionic solid, NaCl, produces Na+ ions (blue) and Cl- ions (green) when dissolved in water.
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The difference in the types of chemical bonds present in NaCl and ethanol is the main reason behind their vastly different melting points and volatility.
What is melting point?
The melting point of a substance is determined by the strength of the forces holding its constituent particles together. In the case of NaCl (table salt), the melting point is very high (801°C) because it has strong ionic bonds between its constituent sodium and chloride ions.
The melting point of a substance is determined by the strength of the forces holding its constituent particles together. In the case of NaCl (table salt), the melting point is very high (801°C) because it has strong ionic bonds between its constituent sodium and chloride ions. These bonds require a large amount of energy to be broken, which is why NaCl has a high melting point.
On the other hand, ethanol is a volatile substance because it has weak intermolecular forces holding its molecules together. Ethanol is a covalent compound, meaning it has atoms held together by sharing electrons rather than by ionic bonds. The intermolecular forces in ethanol are weaker than the ionic bonds in NaCl, which is why ethanol has a low melting point and is more easily vaporized.
The weak intermolecular forces in ethanol are due to the relatively small size of its molecules, which allows them to be easily separated from one another. In contrast, the ionic bonds in NaCl involve the transfer of electrons between much larger ions, resulting in a much stronger attraction between them.
Therefore, the difference in the types of chemical bonds present in NaCl and ethanol is the main reason behind their vastly different melting points and volatility.
To know more about melting point and given link below -
https://brainly.in/question/572447
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