14

Can sugars dissolve in liquid ammonia? Yes, according to Ref.1, liquid ammonia is used to extract sugars in sugar-beet chips: 5.88 kilograms of sugar-beet chips having a moisture content of 5.4 percent and a saccharose content of 68 percent (calculated on the dried substance) are treated in an autoclave of 50-litre capacity with 18 kilograms of liquid ...


7

There are three common classes of methods: Separate the components of the mixture, then detect the amounts of the substances. Use a fancy method that can identify multiple substances in a mixture (such as training a dog to smell different substances, or nuclear magnetic resonance) Use a method that detects only your substance of interest, even when in a ...


6

At very dilute concentrations, the solvating power of water overcomes the natural tendency of surfactant molecules to agglomerate into a separate phase. The shear numerical excess of water molecules just about totally dissociates the bulk surfactant and dissolves it as separate molecules. So a mixture of surfactant and water can be a true solution - clear ...


6

Most likely chromatography. Gas chromatography is often used for detecting volatile compounds. You vaporize the sample at the inlet of a very long, thin tube (the column). The sample then gets pushed along by a carrier gas (the mobile phase). The different components of the mixture interact differently with the stationary phase inside the column and so take ...


6

So it finally turned out to be an artefact, sorry. The probe was protected by a small metallic tube. Somehow water condensed inside. Since this water is isolated from the main liquid, it performed its own phase-transition releasing its latent heat right next to the sensor. The effect was not appreciated when freezing the probe alone. I don't know why, maybe ...


5

To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true: $$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$ The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{...


5

To understand why non - ideal mixtures form azeotropes, we need to understand what is ideal mixture. If you have a liquid mixture of two components A and B, ideal mixture is a mixture in which heterogeneous interactions (A - B) are the same as the average homogeneous (A - A and B - B). This means when you mix components A and B, they don't "feel" ...


5

In the case of magnesium chromate, good solubility in water has been known since 1931. From Hill et al. [1], citing [2]: The only figure on the solubility of the salt [as of 1940] appears to be that of Kohlraush[2], who reported that at 18°[C] 100 ml of saturated solution contained 60 g of magnesium chromate. Most of the other compounds listed, as ...


5

Dilution ratio 1 : N has 2 different, conflicting meanings: (1) The ratio of the 2 mixed volumes ( typical for 1 : 1 to 1 : 3, for everyday/household chemistry ) (2) The ratio of the final and initial concentrations (typical for 1 : 5 and more, for using calibrated volumes and exact concentrations ). Consult the context of your question, but the quote ...


4

All strong acids dissociate in water: $\ce{HX + H2O -> H3O+ + X-}$. Metals reacts with hydronium ions, not with a particular acid, e.g. like $\ce{M(s) + 2 H3O+ -> M^2+ + H2(g) + H2O}$. ( With nitric acid, it is more complicated due its reduction to $\ce{NO}$ or $\ce{NO2}$, but it is not important now. ) Metallic cations and acid anions are not paired ...


4

Ignoring the handwritten notes, which are difficult to read (you can use "Markdown" language, instead), your common-sense answers certainly seem correct! To explain the thought-process behind stating the concentration stays the same when splitting a solution, consider that if the ratio of solvent:solute is X, then the ratio of solvent/3:solute/3 is ...


4

Most of the $10$ compounds from your list simply do not exist. This is why they are not reported in your table. For example iron(III) iodide does not exist. When trying to produce it by mixing $\ce{Fe^{3+}}$ and $\ce{I-}$ ions, a redox chemical reaction occurs spontaneously according to : $$\ce{2 Fe^{3+} + 2 I^- -> 2 Fe^{2+} + I2}$$ For the other ...


4

Using NIST Reference Fluid Thermodynamic and Transport Properties Database (REFPROP) – NIST Standard Reference Database 23, Version 9, I estimated the properties of a mixture of $80\ \%$ methane and $20\ \%$ nitrogen (by mass) at a temperature of $T=94\ \mathrm K$ and a pressure of $p=1.467\ \mathrm{bar}$. At this temperature and pressure, the mixture is a ...


4

The equilibrium is independent on the pressure above the liquid because the mechanism of creating it has nothing to do with the other gases above the liquid It may seem intuitive that a higher gas pressure above a liquid would "push" liquid vapour back into the liquid. But not if you understand how gases work or how a liquid/vapour equilibrium is ...


4

Conjugated chains, especially if delocalisation does indeed take place, tend to be flat or at least stiff. This results in a tendency to adhere to each others. In addition, their stiffness also means that not enough conformational space open up upon solubilisation. In order to enhance their solubility, or at least their processability^, flexible chains are ...


3

In chemistry we assume a mixture of two solids as two different phases, which do not interfere with each other and thus, the solid solute in the solid mixture will not interfere with the solid solvent. So, the vapour pressure of the solid solution and solid solvent will always be same. In a similar way, when two immiscible liquids are mixed together, the ...


3

A buffer is a mixture of a weak acid with the conjugate weak base. Is a mixture of $\ce{NH4OH}$ and $\ce{NH4NO3}$ a buffer solution? I have seen some examples with $\ce{NH4OH}$ and $\ce{NH4Cl}$ but never $\ce{NH4NO3}$. Both mixtures contain $\ce{NH4+}$, a weak acid. Where is the conjugate weak base? You can either write $\ce{NH4OH}$ more conventionally (or ...


3

Let consider ratio of N/P. Let fertilizer A has this ratio N/P=a. Let fertilizer B has this ratio N/P=b. Let you want the ratio c, where a < c < b. Then you need to mix A : B in ratio $$\frac{ b - c}{c-a}$$ In the Central Europe with German scientific influence, it is called the "mixing cross rule". Note that you can chose just ratio of 2 ...


3

Colloidal solutions may contain particles made of liquids or of solids. The particles are liquid in substances like mayonnaise or moisturizer, whose particles are droplets of oil (in water) for mayonnaise or droplets of water (in oil) for moisturizer. They can be solid in substances like acrylic paints, where the particles are made of semi-solid paint ...


3

Glycerol has a density $1.263$ g/mL. It is miscible with water in all proportions. So by changing the ratio glycerol:water, you can make a large number of mixtures having all possible densities between $1.263$ and $1.000$ g/mL. And all these mixtures are made of polar molecules. On the other hand, you may make up all sorts of mixtures with non polar ...


3

An acid/base neutralization will create a salt + water. is rather a secondary/junior high school teaching. It is rather $$\ce{AcidA + BaseB <=> BaseA + AcidB}$$ E.g.: $$\ce{NH3(base) + H2O(acid) <=> NH4+(acid) + OH-(base)}$$ When strong bases or acid dissolve in water, they completely dissociate: $$\ce{HCl(g) + H2O ->[H2O] H3O+(aq) + Cl-(aq)}...


3

It is not a messed up cycle. Let's consider what happens with an example. If you heat up a mixture containing $10$% ethanol + $90$% water, the mixture boils at $92$°C, producing a vapor containing $50$% ethanol + $50$% water. With this operation the liquid loses more ethanol than water. So its concentration in ethanol decreases, and it is necessary to heat ...


3

The point of the question is to test your understanding i. of Raoult's law (that increasing the solute concentration decreases the vapor pressure and that the identity of the solute is not important in an ideal solution; the mole fraction of solute determines $\Delta p$: $\Delta p = p-p^\circ = -\chi_\textrm{solute}p^\circ$ ii. that vapor pressure increases ...


3

Determination of residual solvents is a routine exercise in pharmaceutical industries and benzene is one of them. The technique is called gas chromatography. When you have a very complex mixture, such as sunscreen, one might use a technique called headspace gas chromatography. You would heat a sample in a very small tightly closed vial, at a desired ...


3

There are (at least) two reasons to consider: accuracy and precision. Accuracy as in preparing a stem solution of $\pu{100 mL}$ with a balance right to say $\pu{0.1 g}$ or a graduated cylinders right to the full $\pu{1 mL}$ is easier, than for $\pu{20 mL}$. Depending on the class, volumetric flasks may be better in terms of absolute / relative error than ...


3

I assume you consider the saturated vapor pressure at 100% relative humidity. (As at 50% rel.humidity, vapor pressure = 0.5 saturated vapor pressure). Be aware that ability to contain certain amount of vapor, having respective vapor pressure, is property of space, not of a gas. In first approximation, presence of air or other gas has no effect of ...


3

The Lattice and hydration energies applies to cases of dissolution of ionic compounds like $\ce{NaCl}$. For covalent liquid compounds with polar bonds like water, the lattice energy is replaced by the bond dissociation energy. The value of the dissociation energy ( enthalpy ) -- involving hydration -- can be indirectly determined from the temperature ...


2

Diisocyanates are used in some coatings and polymerize in contact with moisture. Flexithane contains a non-reactive polyurethane (already reacted diisocyanate), and so is simply a solution of rubber in a mixture of solvents (SDS: http://www.hmgcoatings.co.uk/msdspdfs/Flexithane.pdf). The literature claims dry to touch in 5 minutes, ready for a second coat in ...


2

The evidence of a positively charged hydronium ion or a simple hydrogen ion comes indirectly from electrolysis experiments. This was demonstrated by Arrhenius more than hundred years ago. When he proposed these ideas during his PhD work, his mentors did not like these ideas which are bothering you now. If we take ultrapure pure water and dip two electrodes ...


2

"Strong stirring" is a rather imprecise term. There is such a thing as too much speed. Rule of thumb for APIs, if you're working with a magnetic stirrer in a round bottomed flask in a lab (rather than in some industrial vessel or pilot plant setup) 350 rpm is too fast (and no, I can't quote a reference on that, it's one of those things you get ...


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