19

This is standard for purifying substances. To wash means to add your product solution to an aqueous solution (or just water, but frequently a saturated solution) to a separatory funnel. After shaking, you drain the lower layer (which is usually aqueous). This process removes water soluble impurities. This is frequently repeated. Drying is accomplished by ...


17

When most people think of the term solvent, a liquid medium comes to mind; however, in the technical sense of the definition, this does not have to be the case. Here is the definition of a solution present in the IUPAC gold book: A liquid or solid phase containing more than one substance, when for convenience one (or more) substance, which is called the ...


11

The SE answers quoted in the comments provide a good broad answer but with respect to the question of aluminium – aluminium will form a blue solution in liquid ammonia following electrolytic reduction of $\ce{AlI3}$ in liquid ammonia according to J. Am. Chem. Soc. 1950, 72 (11), 5178–5180. Europium and ytterbium have also been reported to dissolve in liquid ...


10

(Source: chem.libretexts.org) In the image, we see that for a "real gas" (indicated by non-ideal solution), Henry's law is applicable for $\ce{\chi} << 1$. As, $$\ce{p = K_H \cdot \chi}$$ hence the pressure should be low. Limitations of Henry's law: The pressure should be low and the temperature should be high i.e the gas should behave like ...


10

The solvent of this experiment should be non polar, and may be a hydrocarbon, or a chlorinated hydrocarbon. This organic phase may contain as impurities some acids and other polar substances soluble in water, that should be eliminated. This liquid is then mixed with an aqueous solution of soda $\ce{NaHCO3}$. Aqueous solutions and non polar substances are not ...


5

If you think of Raoult's law as a special case of Henry's law (since in both cases the vapor pressure of a substance is proportional to its mole fraction in solution) then there isn't really a problem. The case you describe where the solute concentration in solution spans the range $\chi=0-1$ and observes the equation $$\chi=\frac{p}{K}$$ where $K$ is equal ...


5

The description you provided is essentially a shorthand for a standard workup procedure. After performing a reaction, one wants to isolate one’s product while removing the catalyst or other reagents and side products that one doesn’t need. For example, in many cross-coupling reactions an inorganic halide salt is an undesired side-product and a base such as ...


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{...


4

Azeotropes do not exist for all non-ideal solvent solutions. All solvent solutions are more or less non-ideal, but not all solvent combinations form azeotropes. E.g. ethanol and isopropanol form azeotropes with water, but methanol does not. Azeotropes exist if there is large enough deviation from the Raoult law. It means if the azeotrope point of the ...


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 ...


3

Your dilution approach can be heavily improved. Rule no. 1: 2+2 $\neq$4 in solution preparation from an analytical chemist's perspective. An extreme example is that you add 50 mL of water+50 mL of ethanol $\neq$ 100 mL solution. If you add a solid NaCl to 1 L of water, the volume may not remain 1 L. It may decrease! Analytical dilutions are always ...


3

The half-equations are not correctly written. There is no Oxygen atom released, and no H atom emitted, as the author proposes. And the cathode does not get 4 electrons, as he or she states. The correct half-equations should be, first at the anode : $$\ce{Pb + SO_4^{2-} -> PbSO4 + 2 e^-}$$ And at the cathode it is : $$\ce{PbO_2 + 4H+ + SO_4^{2-} + 2 e^- ...


3

The dielectric's is effectively a measure of the solvents ability to hold a charge and the Ɛr is a measure of its permittivity. From a chemical perspective the degree of this is inversely proportional to the born energy of an ion (or self ionization energy) so a solvent that is better at holding an electric charge like water will lower the energy ...


3

Equivalent concept is an archaic unit of measurement that was used in chemistry and the biological sciences in the era before researchers knew how to determine the chemical formula for a compound. An equivalent (symbol: officially equiv; unofficially but often Eq) is the amount of a substance that reacts with (or is equivalent to) an arbitrary amount of ...


3

The parameter a in front of √C is empirical. It varies from solute to solute. And yes, the dissociation is complete at infinite dilution. Dissociation is the separation of ions when dissolving a salt in water. If NaCl is dissociated, it yields two independent ions, one Na+ and one Cl− Ionization is what happens when an atom or a molecule looses one electron, ...


3

I'd like to specifically commment on this: According to the NCERT for Class XII, Part I, [pg. 46, para 3][1], In a pure liquid the entire surface is occupied by the molecules of the liquid. If a non-volatile solute is added to a solvent to give a solution [Fig. 2.4.(b)], the vapor pressure of the solution is solely from the solvent ...


3

Edit: Contribution of enthalpy and bond formation Edit 2: Changed the description of entropy After thinking for sometime, I realized that I neglected to mention three things: The Driving force of precipitation reactions depends on the charge and size of the ions which corresponds directly to the magnitude and order of the hydration shells formed upon ...


3

You have replicated electro-rafination of copper. Copper ions from the being dissolved anode are replacing the copper ions being deposited on the cathode. Therefore overall electroneutrality of the solution is kept. The local neutrality is managed by electromigration of both ions $\ce{Cu^2+}$ and $\ce{SO4^2+}$.


3

It is valid for both volatile and nonvolatile solutes, as it refers to the partial vapour pressure, not total vapour pressure. Saying that, note that it applies only on mixtures with ideal behaviour, as there are many more or less significant positive and negative deviations from the law. These deviations relate to preference of intermolecular bonding to ...


3

For solvent at temperature $T$, surface area $A$ and having the molar fraction $x$, the rate of molecules leaving liquid is: $$\frac {\mathrm{d}n}{\mathrm{d}t}=-C_1 \cdot A \cdot x \cdot f(T)$$ Lower molar fraction means lower surface density and lower evaporation rate per surface area. Factor $C_1$ includes pure solvent molecular surface density and $f(T)$ ...


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

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

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 ...


2

Using dimensional analysis, we get $$\frac{1 \ \text{g}}{58.44 \ \text{g mol$^{-1}$}} = 0.017 \ \text{mol}$$ $$(0.017 \ \text{mol})(6.022 \times 10^{23} \ \text{mol$^{-1}$}) = 1.02 \times 10^{22}$$


2

Binary Mixture Which is an Ideal Liquid Well let's start with what an ideal liquid binary mixture would be. An ideal liquid binary mixture would obey Raoult's law as shown in the figure below from the Wikipedia article. A ideal liquid is a special cases of Raoult's law where the mole fraction of both phases form a straight line from the boiling point of A ...


2

Recall the fundamental properties of the logarithm $$+\log \left(\frac{a}{b}\right)$$ is the same as $$-\log \left(\frac{b}{a}\right)$$ so Henderson Hasselbach can have plus or minus signs. The correct equation is $$\mathrm{pH} = \mathrm{p}K_\mathrm{a} + \log \left(\frac{\text{conjugate base}}{\text{acid}}\right)$$ or $$\mathrm{pH} = \mathrm{p}K_\...


2

Homogenity/heterogenity is a conditional parameter. Homogenity means that at given scale, resolution or sensitivity, you cannot tell the difference in properties in different places within the mixture. Sand dunes are homogenous mixture, seen from far enough. Any matter is heterogenous, if observed at atomic level, because of its non-continuous, atom based ...


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