# All Questions

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### Transition element

Now A transition element is one which forms one or more stable ions which have partially filled d-orbitals. Maganase (Mn) could have an oxidation state of 7+ which means that it will lose all of the ...
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### Why do dianions (such as malonate) bind cations more strongly than anions?

Why does a dianion (such as malonate) bind cations more strongly than its equivalent anion (acetate)? Is it simply because of the proximal availability of another O- group that can bind to cations? ...
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### Fluctuations in Solubility Curve

Why do some solubility curves fluctuate so much with pressure or temperature? Is this due to individual chemical reactions that happen at various temperatures?
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### if we given you a compound ,how to detect it is acid or base or neutral [on hold]

if we give you a compound , how to detect it is acid or base or neutral
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### solubility of Microcrystalline cellulose [on hold]

Greetings.myself sathish from india. TodayToday i have tried to dissolve the MCC and one drug substance in schwiezers reagent. MCC is dissolved but the drug substance cannot. i want to wash schwiezers ...
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### What is the molar mass of vitamin d? [on hold]

Chemistry Project Help for my project. Need answers to questions please !
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### Double Replacement Reactions form Precipitates

Why do most all double replacement reactions result in a precipitate and an aqueous molecule? Is it because the individual solute molecules always form stronger bonds such as how in single replacement ...
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### Speeding up chemical reactions in cold temperatures [on hold]

I know chemical reactions are slowed down in colder temperatures, but what catalyst can be added to speed up the chemical reaction process in colder temperatures (−60 °C to −10 °C)?
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### Calculating pH for titration of weak base with strong acid

Calculate the pH at the equivalence point for the titration of 0.130 M methylamine ($\ce{CH3NH2}$) with 0.130 M $\ce{HCl}$. The Kb of methylamine is ${5.0×10^{–4}}$. So I started with the equation: ...
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### What concentration of Cl2 is present at equilibrium? [on hold]

one mole of chlorine and one mole of bromine are enclosed in a 8 L flask and allowed to reach equilibrium at a certain temp. The reaction is Cl2 (g) + Br2 (g) <----> 2BrCl (g) Kc=11.57x10^-2 at ...
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### How quickly does sulfur hexafluoride mix with the atmosphere?

A common science demonstration is to float a "boat" on sulfur hexafluoride. How long would the sulfur hexafluoride stay in the container (in the experiment linked above) if the container were to be ...
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### Webpage that can help me improve chemistry [on hold]

I'm currently in med univeristy and this second semester we started organic chemistry. We are working with John mccyrry's book. I'm here to ask if you can suggest me any website containing solved ...
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### hydrazine reacts with $\ce{K2Cr2O7}$ [on hold]

what happens ,when hydrazine reacts with $\ce{K2Cr2O7}$ in acidic medium?
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### 'Emulating' calcium hydroxide

I posed this question at the Seasoned Advice SE and thought I might get some more information here. Traditionally prepared corn is cooked in a calcium hydroxide solution to make it more digestible, ...
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volume of gas adsorbed by 1g of activated charcoal at 298K and 1atm pressure follows the order $\ce{NH3}$ > $\ce{CO2}$ > $\ce{CH4}$ > $\ce{H2}$ $\ce{CO2}$ > $\ce{NH3}$ > $\ce{H2}$ > $\ce{CH4}$ ...
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### Why is fat nonpolar?

Why is fat nonpolar while water is polar? In water there is the $\ce{H-O}$ bond and the $\ce{O}$ is more negative, we have $\text{dipole = charge}* \text{distance}$ A fat molecule is like ...
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### Kinetics where RDS is step 1

Hello, In this kinetics problem Im stuck on how to make my answer simplify to the one given in the question. In this particular part I don't think we use a steady state approximation as there is a ...
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### Why does egg yolk turn white when washed with water?

I recently noticed that whenever I washed the egg yolk stuck on some utensils the water becomes milky white. It has to be the egg yolk that turns white and give off the white color to water right?
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### Can any atom donate more than 1 lone pair as a coordinate bond to the same metal?

This would mean the formation of a sigma and one or two pi bonds, all coordinate. I haven't heard of this happening, like fluorine anion or water with 2 lone pairs on O will donate only one lone pair, ...
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### UV-Vis emission from charge-separated states?

Are there examples of UV-Vis emission from charge-separated states? The cases I have encountered have only absorption. Is the recombination process of a nonradiative kind by necessity?
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### What mass of aromatics does a cubic meter of air contain near an oven?

What mass of aromatics are airborne in scented environments for example in a perfume deparment? What is the minimum g/m3 of aromatics that a human can detect, and how much is present when it ...
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### Strong and weak bases? [duplicate]

I have read that a strong base fully dissociates in aqueous solution to form hydroxide ions, and therefore that strong bases are alkalis. I was wondering if you can have a strong base that is not an ...
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### Concentration cell lower half cell concentration from measured cell potential

I am trying to find the Ksp of silver thiocyanate: AgSCN(s) --> Ag+ (aq)SCN-(aq) but I need to first prove that the lower [Ag+] = 1.27-12 M, but don't know how to find it. The data I am given: ...
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### Why does an increase in temperature decrease the EP?

according to the nerst equation, The electrode potential is the SEP minus RT/nF ln([m]/[mn+]). Question is, why? Assuming a simple galvanic cell, we know that in general if the temperature is ...
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### Products of sodium borate and glycollic acid reaction in the presence of water and sodium bicarbonate [on hold]

$\ce{Na2B4O7 + 10H2O + C2H4O3 + Na HCO3 -> } \text{haven't done that in years}$ Basicly the title... I need to help someone with that... But I haven't done it in years... Can someone help me solve ...
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### Carbonyl electrophilic reactivity

Hi there, i would like to ask about the rate of hydrolysis for these compounds A to D. I know that hydrolysis depends on the positive charge of the carbonyl carbon and also the substituent around it ...
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### Why heat of reaction under neither constant pressure or constant volume is considered (in my textbook, or probably somewhere else)?

So my textbook gives me this random equation: $\Delta U = q + w$. Then consider two conditions, under constant pressure and under constant volume. Because $w = -P\Delta V$, constant volume will make ...
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### When and why do hot material take heat from cold material?

This is what I read on Chemwiki: Rudolf Clausius was a German physicist, and he developed the Clausius statement, which says "Heat generally cannot flow spontaneously from a material at a lower ...
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### Preparing a buffer from benzoic acid and sodium benzoate

The question is: "You need to prepare 100.0 mL of a pH=4.00 buffer solution using 0.100 M benzoic acid (pKa = 4.20) and 0.180 M sodium benzoate. How much of each solution should be mixed to prepare ...
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### How is the pKa of extremely weak acids determined?

According to Wikipedia the conjugate acid of LDA has a pKa of about 35 - which is in line with figures I've seen elsewhere. How then can such a weak acid's pKa of be determined? If the determination ...
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### How to measure band gap of powder sample with using diffuse reflectance method

We have UV SHİMADZU 2550 and its diffuse reflectance attachment. I want to measure band gap of single crystal samples. What should I do? Which formulas should I use to calculate band gap? I don't have ...
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### Metallic bonding

Can we picture metallic bonding as an equilibrium between electrons and cations . Suppose:
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### Structure of a Metal in gas phase

If we have a metal in gas phase. Suppose lets say Aluminum. Aluminum has delocalised electrons. There is Al cation -electron attraction in it. Its easier to visualize Al atomic structure in solid ...
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### Can we prolong life? [on hold]

This is rather a bunch of questions that I decided to post on Chemistry StackExchange since I thought the chemists would have the most knowledge about the chemical processes of life. So recently I ...
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### Confused about strong/weak dibasic and tribasic acids?

I know that sulfuric acid is considered a strong acid, and the dissociation of its first H+ ion is complete and of its second H+ ion is partial. Phosphoric acid is weak and all three of its H+ ions ...
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### Products of haloform reaction of acetylacetone?

I searched a lot to find the products of the haloform reaction of acetylacetone, but I didn't find any result. What are the products of the haloform reaction of acetylacetone?
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### How hydrate isomerism results difference in colours?

The standard example is $\ce{CrCl3.6H2O}$, which can have three distinctly different crystalline compounds now known as $\ce{[Cr(H2O)6]Cl3}$ (violet), $\ce{[CrCl(H2O)5]Cl .H2O}$ (blue-green), and ...
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### The concentration is unity! Why? [duplicate]

I want to know why concentration of solids and liquids are taken unity in expression of equilibrium constant( heterogenous equilibrium). It is usually mentioned that the density of solids and liquids( ...
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### Sodium thiosulfate formation

I have a problem solivng this chemical problem. Any help would be highly appreciative. Sodium Thiosulfate can be made by the reaction $\ce{Na_2CO_3 + 2Na_2S + 4SO_2 -> 3Na_2S_2O_3 + CO_2}$ ...
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### Why do exam questions specify “dilute acid”?

All of the exams that I've sat so far, and the homework questions I've had, always ask for the reaction between a substance and a dilute acid. Is there a difference in the reaction between a dilute ...
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### Why do many hypervalant chemicals have non-constant bond angles?

According to the VSEPR model, when a molecule in formed in the shape of $\ce{AB_{x}}$, like $\ce{IF7}$, $\ce{SCl6}$, and $\ce{PCl5}$, its structure is found by reducing the repulsions between ...
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### What is the highest possible expanded octet?

Often called "hypervalent", chemicals like Phosphorous Pentachloride and Sulfur Hexaflouride are possible due to the fact that their central atoms form covalent bonds with more than four other atoms, ...
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### Raoult's Law explained with thermodynamics/ free energy

I got some confusion going on with this explanation of Raoult's Law. This is what my book say: Because the ideal solution has a higher entropy than the pure solvent, the energy of a vapor ...
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### Reduction of acids with borane

What is the mechanism of the reduction of organic acids with borane? Borane reductions don't work well with electron deficient carbonyl groups. Why is that so, and how isn't the carboxyl group an ...
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### Molecular weight determination from freezing point depression

I have these two questions in my lab manual and I don't know how to approach them. 1) Which is the better solvent for molar mass determinations by freezing point depression, benzene or cyclohexane? ...
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### What is the rate of analysis of hydrogen peroxide?

I'm kind of stuck on this problem: What is the rate of analysis of hydrogen peroxide, if the molar concentration of hydrogen peroxide decreased from 0.85 mol.dm^-3 to 0.45 mol.dm^-3 in two ...
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### Why are so many wave functions associated with hydrogen?

According to Wikipedia, there's an infinite set of possible wavefunctions (orbitals) for the hydrogen atom: \psi_{n\ell m}(r,\theta,\phi) = \sqrt {{\left ( \frac{2}{n a_0} \right ...
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### Organic Chemistry - strongest acid [on hold]

Hello Friends of Orgo Chemistry! I found this question in my Organic Chemistry Book. And I tried answering, but for some reason I just cannot figure it out. I even looked into the solutions and I ...
Which one of the following substituents at para-position is least effective in stabilizing the phenoxide ion $\ce{PhO-}$ (a)$\ce{-CH3}$ (b)$\ce{-OCH3}$ (c)$\ce{-COCH3}$ ...