# Tag Info

19

Many volatile liquids are not combustible Dichloromethane (DCM) is a widely used solvent by chemists. It boils at around 40°C (the same as diethyl ether) but is not remotely combustible or flammable. Ether is both very volatile and very flammable, so much so that most labs would prefer not to have it used anywhere where flames or sparks could be present. ...

18

Vapor is a much older word alluding to dampness and it was not coined by scientists. It is in use since the 1300s. The actual meaning of meaning of vapor is "Matter in the form of a steamy or imperceptible exhalation; esp. the form into which liquids are naturally converted by the action of a sufficient degree of heat. This is the original 13th century ...

17

There's a NASA report that looks into this: "ON THE SOLUBILITIES AND RATES OF SOLUTION OF GASES IN LIQUID METHANE", Hibbard and Evans, 1968 and concludes that such mixtures are possible. Starting on page 8: Figure 5(a) presents the curves for oxygen, argon, carbon monoxide, and nitrogen. Also shown are the two experimental values for nitrogen. ...

17

Isopentane $\ce{C5H12}$ has the density of $0.6201~\mathrm{g\,cm^{-3}}$ at $20~\mathrm{^\circ C}$ [1, p. 3-330]. References Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; CRC Press, 2017; Vol. 97. ISBN 978-1-4987-5429-3.

16

The critical point is a point of convergence of all state properties of the respective liquid and gas. It can be considered as the degeneration point, where there is no difference between gas and liquid and this distinguishing does not make sense any more. It can be also said the supercritical fluid near the critical point is neither gas neither liquid. It ...

14

It really does liquefy. But it does not do so in exactly the same way as you see below the critical temperature and pressure. As an example, suppose you heat steam to 400°C and then compress it, isothermally, to 5000 bars pressure*. When you are done, you find that the water has a density and viscosity more or less similar to ordinary liquid water; what ...

14

The normal use distinguishes "vapour" from permanent gas At normal lab conditions there is a (fairly obvious) distinction between things that could exist as liquids and things where no liquid phase is possible. Oxygen, for example, is a permanent gas, but dichloromethane is not. But the vapour pressure of dichloromethane is pretty high and there ...

12

Volatility ( even if by thermal decomposition ) is the necessary, but not sufficient condition for liquids to be combusted, forming a flame. Liquid helium is the most volatile liquid ever, but there is no way to burn it ( chemically ). As other answers mention, there is correlation, as flammable liquids are generally less polar and more volatile than polar ...

12

To add to the Bob's excellent answer (and expand a bit on my comment there), I've found two other potentially interesting papers to peruse. The first is R.J. Hodges and R.J. Burch, Cryogenics 7 112-113 (1967), titled "The equilibrium distribution of methane between the liquid and vapour phases of oxygen". They note a "very high solubility of methane in ...

10

Caesium salts are unapologetically ionic, and they typically have quite high mass solubilities in many solvents, including water. Assuming organic ions are allowed, caesium acetate ($\ce{H3CCO2^-Cs+}$) in particular has a remarkably high solubility of 9451 g/kg water at −2.5 °C, increasing to 13 455 g/L water at 88.5 °C. Caesium formate ($\ce{HCO2^-Cs+}$) ...

10

I'm surprised the OED has such a strict definition for gas. I could not find a strict definition in the IUPAC color books (certainly not in the gold book). Presumably these words are in such common use that their definition is assumed understood or easily found. The analytical compendium (orange book) and physical chemistry book (green book) mention vapour (...

9

According to Hans Jaffe: Eine metallische Verbindung von Lithium mit Ammoniak. Elektrische Leitfähigkeit und galvanomagnetische Effekte. Z. Physik 93, 741–761 (1935) https://doi.org/10.1007/BF01337859 the saturated solution of lithium in liquid ammonia (approx. $\ce{4NH3 \cdot Li}$) has a boiling point above RT, and is significantly less dense (=0.48g/ml) ...

9

The following data is compiled from [1, pp. 4-44, 5-167]: Table 1. Selected solubility values of the inorganic compounds with significant ionic character at $25~\mathrm{^\circ C}$. $$\begin{array}{lc} \hline \text{Formula} & \text{Solubility in water}/\pu{g L-1}\\ \hline \ce{CsF} & 5730\\ \ce{SbF3} & 4920\\ \ce{LiClO3} & 4587\\ \ce{Pb(ClO4)... 8 There is not going to be a single definitive answer, primarily because of a wide gray zone surrounding the domain of ionic compounds. Besides, as Nikolau noted, the question is ambiguous. If you want mass concentration, then look at \ce{InI3} which claims a whopping 13100~\mathrm{g/L}. Pity that it is probably ionic in name only, judging by the ... 8 The \ce{CO2} exists in two phases when you buy a partially-filled \ce{CO2} cylinder because there is extra volume (which is needed to allow expansion as the container warms). Therefore, the pressure in the container is not 100 bar, but closer to 80 bar at 293K. If the container had only enough room for the \ce{CO2}(l), then, indeed, there could be no ... 7 Not always true. Tetrachloroethylene ("perc", as it is sometimes called in the dry cleaning business) is not inflammable, but quite volatile. Carbon tetrachloride, which was also a common solvent some decades ago, is yet another halocarbon solvent that is volatile, but not inflammable (hence its former use in fire extinguishers). In general, volatility and ... 7 Not all data are provided in explicit form. They are often not frequently needed and can be often deduced from other data with using of high school knowledge. You can calculate the volume occupied by 1 water molecule ( in average ) from the water molar mass \pu{M}, water density \pu{\rho} and the Avogadro constant N_\mathrm{A} as$$V=\dfrac{M}{\rho \...

6

"Sealed in a vacuum" is an oxymoron, a contradiction in terms, much like "frozen with fire". If you seal a liquid in a flask containing nothing else but vacuum, then a part of the liquid will quickly evaporate and fill the flask with vapor, so it would no longer be a vacuum. The said vapor will exert some pressure, depending on the temperature and the ...

6

the graph is trying to show three things (pressure, density and temperature) in 2D. The yellow portion shows the super critical fluid of $\ce{CO2}$. The blue portion liquid $\ce{CO2}$ The light green portion shows the gas phase for $\ce{CO2}$. The horizontal lines are called "tie lines." The two phases at the ends of the tie lines are in equilibrium. ...

6

The horizontal lines represent a combination of liquid and vapor at the same temperature and pressure. At the left of the horizontal line is the liquid specific volume and on the right side is the saturated vapor specific volume. Locations between the two ends represent the specific volume of the combination, which is proportional to the amount of each.

6

In college, I had a thermodynamics teacher who was awesome. He had a way of explaining things that were accurate and easy to understand. He explained this difference to us this way: A gas will not condense into a liquid with an isothermal compression. (i.e. an Ideal Gas) A vapor will form liquid when isothermally compressed. His example: When you boil water, ...

6

tl;dr– "Gas" and "vapor" aren't mutually exclusive. Generally: a gas is any material that'd fill a volume to its boundaries; and a vapor is a gas-like material that's associated with a condensed-state transition. It's a bit misleading for a state-diagram to label a region "vapor" in a manner that might imply that a vapor's ...

5

The horizontal lines are tie-lines, as explained in another answer, but between gas and liquid $\ce{CO_2}$. Note the curves labeled with temperatures lie below the critical temperature and above the triple point. The horizontal lines therefore represent regions where gas and liquid $\ce{CO_2}$ coexist. The single point at the cusp of the dotted line is the ...

4

When you heat up a liquid at constant volume (leaving sufficient space for the gas phase), the density of the liquid will decrease and the intermolecular interactions will weaken. Some of the liquid will transition to vapor, so the vapor above the liquid will get denser and the frequency of intermolecular interactions will increase (it behaves less and less ...

4

Take four test tubes with sample, add bromothymol blue in two of them, methyl red in the rest. Add a few drops of HCl to one of the BTB tubes, and a few drops of NaOH in one of those with methyl red. One of the tubes will have a noticable change of colour.

4

When we talk about energy bands, we are talking about mixing of orbitals on different atoms (AOs) with similar energies. First, assume simple models. In the solid, the structure is very regular and all atoms have AOs with identical matching energies. This makes the number of orbitals available for mixing in solids very large, and mixing results in bands. In ...

3

Use the ebullioscopic equation (the first equation) in this Wikipedia article, $$\Delta T = K_\mathrm{b} m$$ First solve for $m_\mathrm{init}$, the initial molality of urea. Second figure out at what molality $m_\mathrm{fin}$ the boiling point is elevated by $\Delta T = \pu{1.5 °C}.$ Since the amount of urea is constant, the % change in the mass of water ...

3

One of the best websites for all advanced water properties is a website maintained by Dr. Martin Chaplin http://www1.lsbu.ac.uk/water/physical_anomalies.html#Pvisc Keep in mind that viscosity is a really complicated subject and water is among the unique solvents. In general viscosity of liquids increases with pressure. At pressure extremes, let us say, 100,...

3

You may look at silicon Si and its derivatives. For example, the ethoxytriethylsilicane, or triethylsilicol ethyl ether is boiling at 153 °C. Or the tetraethylsilicane is also boiling at 153 °C. This last substance is used as a reference in NMR spectroscopy.

3

The nearest to an ideal fluid is a hard sphere fluid, but this is removed from the ideal gas or even solution concept of ideality in a critical way. Ideal (also called perfect) gases are ideal because they lack intermolecular interactions. A statistical description that ignores the intermolecular potential suffices to describe an ideal gas. A first ...

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