Questions tagged [boiling-point]

The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid

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19
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Melting and boiling point trend in Group II

The following picture shows the melting and boiling point trends down group II elements. I have added question marks where the variability in data was rather disturbing (over two hundred degrees ...
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Why do chlorinated silanes have lower boiling points than their methane analogs?

The boiling points of the chlorinated silanes and methanes are given below: $$\begin{array}{ccc} \hline \text{Species} & \text{Boiling point (X = Si) / }\mathrm{^\circ C} & \text{Boiling ...
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Why are branched isomers less polarisable?

This fact was given as an explanation as to why branched isomers of a compound have lower boiling points. How are branched isomers less polarisable and how does this relate to London dispersion ...
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How can a substance have a higher boiling point but lower melting point than another substance?

Looking at 1,3-Butadiene and Isoprene, I'm wondering: why does Isoprene have a higher boiling point, but a lower melting point than 1,3-Butadiene? I'm thinking this might be because the Methyl group ...
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42 views

Order of boiling point of group 14 halides

Find out the species having lowest boiling point: (A) $\ce{SnCl4}$ (B) $\ce{GeCl4}$ (C) $\ce{SiCl4}$ (D) $\ce{CCl4}$ I have considered the inert pair effect of $\ce{Sn}$ here which will make the ...
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35 views

Boiling points of ethylene, formaldehyde and oxygen

The boiling points of ethylene, formaldehyde and dioxygen are $\pu{-103.7 ^\circ C}$, $\pu{-19 ^\circ C}$, and $\pu{−183 ^\circ C}$, respectively. I expect formaldehyde to have the highest boiling ...
2
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0answers
102 views

Why does hydrazine have a higher boiling point than water?

$\ce{N2H4}$ has a boiling point of 114 °C, which is higher than the boiling point of water. Why is this so? Both $\ce{N2H4}$ and $\ce{H2O}$ have two lone pairs, so the number of hydrogen bonds per ...
2
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55 views

Why don’t compounds with high boiling points not necessarily have high attraction constants (a) in the Van der Waals equation?

You can find a list of constants $a$ and $b$ for the van der Waals equation in a Wikipedia website. Accordingly, hexane has a higher attraction constant ($a$) than that for water (24.71 vs 5.536), but ...
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0answers
1k views

Why is the boiling point of para hydroxybenzoic acid lower than that of ortho hydroxybenzoic acid?

As per the literature at 760mm of mercury, p-hydroxy benzoic acid has lower boiling point ($\pu{336^\circ C}$ - ChemSpider) than o-hydroxy benzoic acid ($\pu{372^\circ C}$ - ChemSpider). What is the ...
2
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306 views

For a given period, why is the boiling point of the halogen greater than that of the noble gas?

The boiling point of bromine, a halogen, is $\pu{58.8^\circ C}$, while the boiling point of krypton, the noble gas in the same period as bromine, is $\pu{-153.4 ^\circ C}$. I thought that the larger ...
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96 views

Boiling Point trend

Why does group 13 and 14 show reverse the trend of boiling point? In other groups, boiling point increases down the group but here it decreases.
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830 views

Dissociation of H3PO4 and colligative properties

Which of the following solutions that have concentrations of $0.01\ \mathrm{M}$ show the highest elevation in boiling point and why? A) $\ce{NaCl}$ B) $\ce{CaCl2}$ C) $\ce{H3PO4 }$ D) $\ce{C6H12O6}$ (...
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519 views

Why does cooking oil lower the vapor pressure of water?

I added different amounts of oil to different containers with 50mL of water and weighted the containers. Then I heated the containers for 15 minutes in a water bath and weighted again. I noticed that ...
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2k views

Why there is an exception in melting and boiling point in p block?

Why is the boiling point and melting point of 15th group and 16th group has an exception? We know that as molecular mass increases boiling point and melting point also increase. So, down the group 15 ...
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31 views

Boilling colloidal silver?

I have some colloidal silver that i bought from a shop. It is 18ppm, however, I need a higher PPM and I can't seem to buy it anywhere where I live. If I boil this colloidal silver, would it make the ...
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3answers
109 views

Why is the boiling point of trichlorofluoromethane lower than that of chloroform?

If $\ce{CFCl3}$ has a higher molar mass, how come $\ce{CHCl3}$ has a higher boiling point? $$ \begin{align} \mathrm{bp}(\ce{CFCl3}) &= \pu{23.77 °C} \\ \mathrm{bp}(\ce{CHCl3}) &= \pu{61.15 °C} ...
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226 views

Why does chlorine gas have a higher boiling point than hydrogen iodide

Hydrogen iodide, $\ce{HI}$, is a dipolar molecule much larger than chlorine, $\ce{Cl2}$. The melting point of $\ce{HI}$ $(222.35\ \mathrm K)$ is definitely higher than that of $\ce{Cl2}$ $(171.6\ \...
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463 views

Molar entropy of vaporization

If a substance has a molar heat of vaporization of $\pu{3.05\times10^4J/mol}$ and a normal boiling temperature of $\pu{80.0^\circ C}$, what is the value of its molar entropy of vaporization $\Delta S_\...
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2k views

Explain the effect of intramolecular hydrogen bonding on solubilities in cold and hot water?

There is a statement given in my textbook (Cengage, Organic Chemistry (Part 1), page 4.33) which is as follows: (I edited the statement to make it simpler) One can account for the solubilities of ...
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287 views

Can someone explain me the difference in boiling point of water when I add: KBr; CaCl2; AlCl3?

I have noticed (during an experiment) that the boiling point of the solutions created by H2O+KBr; H2O+CaCl2 and H2O+AlCl3 see their boiling point increase. During the experiment, I thought that, ...
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257 views

What are the factors affecting Boiling Point in Ions?

I understand that for molecular substances, intermolecular forces such as van der Waals forces and hydrogen bonding are the major factors effecting the boiling point. However, I am not sure about ...
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84 views

Vapor pressure, volume and boling point

The saturated vapor pressure is designated as the gas pressure in a closed container when the evaporation process has reached an equilibrium (when there are as many molecules returning to the liquid ...
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1k views

What is the temperature at which lava evaporates?

According to this article -> http://ntrs.nasa.gov/search.jsp?R=19660041998 Lava evaporates under natural conditions, but apparently, only a little bit. I'd like to know the temperature at which ...
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Difference in the boiling point of piperidine and cyclohexanamine

The reason that I believe must be the difference in the amount of hydrogen bonding formed by both of the compounds in the liquid . But I suspected that both must be having same amount of hydrogen ...
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Why change on pressure affects the boiling point much more than the freezing point?

I do see the mathematical solution given by the classius clapyeron equation but is there any real life and intuitive expalanation?
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94 views

When exactly does the first drop of distillate appear in a distillation?

The below image (source: here) is from a fractional distillation of a mixture of two liquids, one with a boiling point of 69 degrees celsius and the other with a boiling point of 98 degrees celsius. ...
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63 views

Should High Vacuum oil smell?

I recently have purchased a high vacuum pump and am currently repairing it, the internals have a strong smell of oil. I was going to do an oil change anyway but should I clean all the old oil. High ...
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450 views

Do mixtures have a boiling point?

Let's assume a mixture which can be heated without decomposing. This site explains that while pure substances have a sharply defined melting point and boiling point, mixtures tend to have a melting ...
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713 views

Polarisability of alkynes, alkenes and alkanes

I have noted a little trend in the boiling points of alkynes, alkenes and alkanes. Upon searching for the explanation, I have chanced upon an answer written by M.A.R. (Alkane, Alkene, Alkyne boiling ...
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180 views

Boiling points of Hydroxylamine and water

Why does $\ce{NH2OH}$ have a lower boiling point than water? According to Wikipedia, hydroxyamine has a boiling point of 58 °C. Could this be due to the extent of hydrogen bonding among both molecules?...
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Boiling Point Reversal

If substance A boils at a lower Temperature than substance B under atm. pressure, can it be that under some other condition, say, elevated Pressure or under vacuum a reversal of the trend occurs? i.e....
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1answer
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Calculating Boiling Point of solution

I wish to calculate the boiling point of the following solution. (w/w) 78.8% Glycerol, 11.6% Propylene Glycol, 8.3% Water, 1.2% Nicotine (molar fraction) 0.5790 Glycerol, 0.1037 Propylene Glycol, ...
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2answers
634 views

Ordering compounds by boiling points

Here is a MC question from my chemistry professor: What is the correct order of boiling points for molecules: $\ce{CO2}$, $\ce{LiOH}$, $\ce{CH3OH}$, $\ce{CH2O}$? I am mainly confused about ...
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2answers
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Can somebody help me understand this sentence?

"The molar enthalpy of vaporisation of a liquid is the enthalpy change when one mole of the liquid changes into one mole of its gas at the boiling temperature." The part which i am not sure of is the ...