Questions tagged [mixtures]

Questions related to the physical combination of two or more substances on which the identities are retained and are mixed in the form of solutions, suspensions, and colloids.

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6 votes
1 answer
965 views

What is 'spray foam' or 'expanding foam'?

At the wikipedia are: Spray foam (expanding foam in the UK) is a chemical product created by two materials, isocyanate and polyol resin, which react when mixed with each other and expand up to 30-60 ...
5 votes
2 answers
2k views

A solution is cloudy at lower concentration and becomes clear at higher concentration. Why?

This might be just an "everyday life science" question. I am a university professor but not in chemistry so please educate me. Today I was adding some floor cleaner formula to water as ...
2 votes
1 answer
107 views

Question about chemical potential of a multicomponent ideal gas

Consider a pure ideal gas, i.e. only having one component. The chemical potential and free energy of this gas are as follows: $$\mu_1=\mu^\circ(T)+RT\ln\left(P\right)$$ $$G_1=n\mu_1$$ Where n is the ...
1 vote
1 answer
55 views

Determination of the composition of the mixture based on acid-base titration

The solution can contain $\ce{HCl}$, $\ce{H3PO4}$ or $\ce{NaH2PO4}$ individually or in all possible combinations. An aliquot of $25.00\,\text{mL}$ of this solution consumes $14.56\,\text{mL}$ of $0....
1 vote
0 answers
30 views

Estimation methods for temperature evolution of a high $\Delta H_{mix}$ dilution ($\ce{KOH}$ in water)

Question up front: Can temperature evolution in solutions be short-hand-estimated by simple state based calculations - with reasonable expectations of precision? (+/- 10° C) I am trying to calculate ...
0 votes
0 answers
29 views

What is the most accurate way to determine the amount of water in a material from XRF and LOD-105 results?

this might seem like a silly question but I want to be sure. I have the results from an external laboratory for the bulk chemical composition (by XRF) and moisture (by Loss on Drying to 105 degrees ...
1 vote
0 answers
49 views

History of Azeotrope (azeotropic mixtures)

I'm currently researching the history of azeotropic mixtures for an essay, and I've come across some interesting information. The term "azeotrope" was coined in 1911 by English chemists John ...
-1 votes
1 answer
151 views

Does the equilibrium constant of an ideal liquid mixture reaction depend on pressure?

I want to calculate the equilibrium constant K[T] for a the following reaction: $$\ce{CH3OH(l) + C4H8(l) -> C5H12O(l)}$$ It is assumed that the mixture is ideal and the reaction takes place at 14 ...
2 votes
2 answers
240 views

How does steam distillation work to extract a substance from a mixture, below its boiling point?

This is a small confusion I have regarding steam distillation. Let us consider a sample of water mixed with an organic compound that is insoluble in water. Let us also consider that the boiling point ...
-4 votes
2 answers
84 views

Does emulsify mean to combine or break down?

In chemistry, emulsification is defined as the "an additive which helps two liquids mix" (Source: Wikipedia), "a mixture of two or more liquids that are normally immiscible owing to ...
2 votes
0 answers
26 views

Creation of a Solution of Liquid Latex + Sodium Caseinate with Polyvinyl Alcohol

I am going to be experimenting with creating different types of liquid latex formulations, primarily for the purposes of increasing shear strength and tear resistance, as well as just general ...
4 votes
1 answer
1k views

Why is glass a mixture and not a solution?

While studying mixtures and solutions, I read that glass is a mixture and not a solution. Then I searched over the Internet about it, but I got the same answer that it is a homogenous mixture. But ...
1 vote
1 answer
348 views

Mixture of two ideal gases

Why is $\Delta H_{\mathrm{mix}}=0$ in a mixture of ideal gases? If $\Delta H=\Delta U + \Delta PV $ and I know that in ideal gases there are no interactions between molecules so $\Delta Q=0$ and I ...
19 votes
5 answers
14k views

Un-denaturing industrial alcohol

I have a question regarding the denaturation of industrial ethanol with methanol to discourage its consumption. The boiling point of methanol is 64.7 °C, while the boiling point of ethanol is 78.37 °...
11 votes
2 answers
1k views

Why would there be a non-zero Gibbs energy of mixing for ideal gases?

When two ideal gases $\ce{A}$ and $\ce{B}$ mix, they don't interact. The chemical potential of each gas is independent of the other, e.g. for $\ce{A}$: $$\mu_\ce{A} = \mu_\ce{A}^\circ + R T \ln \frac{...
4 votes
3 answers
637 views

Is the negative excess volume of ethanol/water the cause of my math error?

I have a binary mixture, say ethanol at $90\%wt$ ethanol, $10\%wt$ water. According to Perry's Chemical Engineers' Handbook 9th Ed., that mixture has a density of $0.81797g/cc$ (at $20^{\circ}C$). ...
3 votes
1 answer
293 views

derivation of activity coefficient from Margules laws?

basics In Margules activity model, the excess Gibbs free energy is expressed as: $$ \frac{G^{ex}}{RT}=X_1 X_2 (A_{21} X_1 +A_{12} X_2) + X_1^2 X_2^2 (B_{21}X_1+ B_{12} X_2) + ... $$ meanwhile, we ...
2 votes
0 answers
69 views

How does the Szilard-Einstein refrigerator design evaporate its refrigerant?

In their 1927 patent, Leo Szilard and Albert Einstein use butane as a refrigerant in their non-compressive refrigerator design. In the patent the authors begin the description of the principle of ...
0 votes
1 answer
52 views

Any way to predict what quantities of heptane and chloroform will match the density of water?

I am trying to make a solution of heptane and chloroform that matches the density of water. Is this something which must be done experimentally as it is generally unpredictable? Does a software exist ...
0 votes
1 answer
38 views

Dependence of the permittivity on solvent mixing ratio

I am doing DFT calculations on an organometalloid compound to assess whether it dissociates into an ion pair in different solvents. I suppose that the more polar the solvent is the more stable this ...
0 votes
3 answers
438 views

Is milkshake a heterogeneous mixture?

In my textbook, one of the examples of a heterogeneous mixture is milkshake, I don't see how ? I think the answer depends on the fact that How many phases are there in a milkshake, which I think ...
1 vote
1 answer
357 views

Why water volume went up by almost the same amount after adding salt?

Seems like it's a well-known fact that adding salt to water will not raise the water volume by much (e.g.: Why there is no change in water level when salt is added? ) I've done this experiment at home ...
1 vote
1 answer
57 views

More minerals in seawater at greater depths?

There are lists such as the one below detailing how much of different minerals seawater contains: https://web.stanford.edu/group/Urchin/mineral.html (For instance ) Would you expect this to be the ...
5 votes
3 answers
10k views

What is the entropy of mixing of two ideal gases starting out with different pressures?

The entropy of mixing of ideal gas is given by this equation: $\Delta S_{mix} = -nR(x_1\ln x_1 + x_2\ln x_2)$ Does this equation works only when the initial conditions of both compartments are at ...
12 votes
3 answers
20k views

How does dimethylsulfoxide serve as a cryoprotectant?

In cell culture, dimethylsulfoxide (DMSO) is added to prevent the formation of ice crystals which may lyse the cells. Exactly how does dimethylsulfoxide act as a cryoprotectant?
-3 votes
2 answers
228 views

Calculate the concentration of HF in aqueous solution of NH4F and NH4HF2 mixture

There is a similar question on this site, but here i have a mixture. I have a mixture of NH4F (35% weight) and NH4HF2 (8% weight) in water. How do I calculate the weight % expressed in HF? or the ...
6 votes
3 answers
1k views

Does stoichiometric gas mixture produce the highest explosion pressure (or energy) compared with other explosive limit mixture?

I understand that a stoichiometric mixture contains a balanced mixture of air and fuel and both fuel and air are completed consumed. For example, the ideal stoichiometric mixture for propane is ...
-2 votes
1 answer
280 views

What's the stoichiometric ratio of Kerosene to a mixture of 50% water and 50% hydrogen peroxide [closed]

So I'm wanting to do some testing with combustion of certain liquids, and I'd like to know what the right ratio is for these liquids. What I'm going to be using is regular kerosene (NOT RP-1) and 50% ...
1 vote
1 answer
253 views

What is the composition of air (oxygen and nitrogen) as it is displaced by propane?

We have purchased an oxygen analyzer that is calibrated with pure nitrogen and pure oxygen. It measures 20.91% when it samples air in the atmosphere. The analyzer is reading in %volume. We have built ...
1 vote
1 answer
80 views

How do clay particles form a colloidal mixture?

I have been learning about water coagulation in my chemistry textbook. Apparently, before being treated, water has clay particles, primarily silicates and aluminosilicates, which apparently have a ...
3 votes
3 answers
419 views

How is the entropy of mixing related to chemical reactions in solution?

When calculating the Gibbs energy of reaction for reaction mixtures at arbitrary concentrations, you use the following expression: $$\Delta_\mathrm r G = \Delta_\mathrm r G^\circ + RT\ln Q$$ The term $...
3 votes
1 answer
1k views

Is the entropy change positive or negative in this reaction?

Suppose I have a reversible reaction \begin{align} \ce{A(g) + B(g) <=> C(g)}\\ \end{align} with equilibrium constant K. Its ΔΗ is positive throughout. Now, suppose I start with 1 mole ...
2 votes
0 answers
68 views

Chemical potential vs derivative of free energy

Let $x$ be the concentrations of species in a chemical system, and let $G(x)$ be the Gibbs free energy. My understanding is that the chemical potentials should be given by $$ \mu_k = \frac{\partial G}{...
1 vote
0 answers
66 views

What is the necessary and sufficient condition for a mixture to be ideal?

I am trying to understand some concepts from solution thermodynamics related to ideal mixtures and fugacity. My main question is what is the necessary and sufficient condition for a mixture to be an ...
3 votes
1 answer
164 views

Why does the equation for chemical potential apply to liquids and aqueous solutes?

The equation for chemical potential of a gas can be derived as such: At constant temperature, $$\mathrm dG = V\,\mathrm dP \label{eqn:1}\tag{1}$$ Substituting with the ideal gas law $PV = nRT$, $$\...
1 vote
1 answer
156 views

How to achieve desired response of a non Newtonian fluid prepared from silica nanoparticles and polyethylene glycol (PEG 400)?

I am working on non-newtonian fluid project. I have experimented with cornstarch and water and achieved the consistency desired with 55% cornstarch and 45% water. Now I want to create similar outcome ...
-1 votes
2 answers
123 views

"No heat, light or electrical energy may be evolved or absorbed during the formation of a mixture." What about heat from friction?

I was reading about mixtures in my chemistry textbook. One of the characteristics of mixtures that was stated was "No heat, light or electrical energy may be evolved or absorbed during the ...
0 votes
0 answers
339 views

How do I keep my homemade liquid fabric softener from separating?

I have a recipe for a homemade liquid fabric softener that smells good and works great, but I have to shake it every time before I use it. It gets old fast. The recipe calls for: 12 cups hot water, ...
-2 votes
1 answer
202 views

Find the molarity and molality

We take 10mL of $H_2SO_4$ with a $96\%$ of mass and density $1.84g/cm^3$, and we add it into a flask that has $0.5L$ of capacity, filled up to half of the flask with distilled water. We shake the ...
5 votes
3 answers
2k views

What is the molecular interpretation of Raoult's law?

I was reading about Raoult's law which states: It states that the partial vapour pressure of each component of an ideal mixture of liquids is equal to the vapour pressure of the pure component ...
2 votes
3 answers
2k views

Separating sugar from soda

I want to do a lab with my students in which they will try to prove how much sugar is in a can of coke. I know that distillation is the go-to method for separating out the syrupy sugar mix, but does ...
5 votes
2 answers
787 views

Name of particles in a suspension

What is the proper name given to the particles in a suspension? Suspensae perhaps? When these particles are brought out of suspension, and precipitate down to the bottom of the mixture, what is that ...
13 votes
2 answers
693 views

Do azeotropic mixtures evaporate proportionally?

Do azeotropes evaporate, without boiling, in proportionate amounts, or does this property describe their behaviour only at boiling point? Concretely, if 91% isopropyl alcohol/water (by volume, i.e. an ...
2 votes
1 answer
177 views

Find gas pressures of injection knowing mixture pressure without knowing volume

Let's say we have a gas 1 moving inside a pipe (we don't know the geometry) at mass flow rate $Q_1$ and temperature $T_1.$ We inject a gas 2 at some point inside the pipe with gas 1 at mass flow rate $...
2 votes
2 answers
4k views

Most efficient way to purify household vinegar: distillation or freezing?

I am aware that there are better ways to purify acetic acid out of a water-acid mixture than these, but which one out of distillation (using heat) and fractional freezing (using cold) would gain a ...
0 votes
0 answers
16 views

DI water vs. Tap water in ethanol-water and salt phase change reaction

We did a very simple lab like one you would do in highschool showing that you can seperate the phases of water and ethanol using salt. As simple as it sounds, we could not get it to work no matter ...
1 vote
0 answers
48 views

Why is my ethanol–water mixture showing negative change in enthalpy of mixing? [duplicate]

I am conducting an experiment where I mix two solutions $\text{A}$ and $\text{B}$ and then I am measuring the temperature change (for real solutions, i.e., $\Delta_\mathrm{mix}H\neq 0).$ I took the ...
0 votes
1 answer
5k views

Is the density of a mixture ever just the sum of the densities of each species in the mixture? [closed]

My current hypothesis is that this is true when the volume is finite and perhaps this would cause the densities to be additive. For example, imagine there is a closed container, 2 L in size. And ...
1 vote
0 answers
101 views

Methods of mix thick liquids (3D printer Resin), stir, shake or acoustic?

Most of the 3D printing community mixes resins by hand by simply shaking them. This is not 100% effective (I believe) and also creates a lot of bubbles that get in the prints. What method would you ...
5 votes
1 answer
5k views

Is there anything that doesn't mix with water or oil?

It's well known that water and oil don't mix, and if you put them together, the oil will float on top of the water in a distinct layer. My understanding is that this is because water is polar due to ...

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