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1answer
26k views

Sodium chloride + sulfuric acid [closed]

Why does sulfuric acid displace more volatile acids from salts? My textbook says that sulfuric acid can displace more volatile acids from metal salts. How is $\ce{HCl}$, which is not even a reactant, '...
2
votes
1answer
661 views

Finding partial derivatives for an ideal gas and van der Waals gas

How do I determine $\left({\partial P\over\partial V_\mathrm m}\right)_T$ for an ideal gas and also for a van der Waals gas? Note that $T$ is the only variable which is held constant, and that's my ...
7
votes
1answer
1k views

Which singlet dihalocarbene has the strongest carbon-halogen bond?

There are three singlet carbenes - difluorocarbene, dichlorocarbene and dibromocarbene. Which has the strongest carbon halogen bond? Obviously backbonding is a point to be considered, as carbene is ...
25
votes
1answer
804 views

Do vinyl cations adopt a classical or non-classical structure?

Whilst reading this question today, I remembered something that I had seen previously here. In the second linked question, @Martin provided a reference to suggest that vinyl cations actually adopt a ...
27
votes
2answers
3k views

Which of the following is the more stable carbocation?

Which of the following is the more stable carbocation? I thought the 1st carbocation would be the more stable one as the pi-electron density of phenyl group can overlap with the vacant orbital on ...
18
votes
0answers
3k views

Why is nitrogen dioxide (NO2) brown? [closed]

I don't understand why nitrogen dioxide $\ce{NO2}$ is coloured brown when nitrate $\ce{NO2-}$ and dinitrogen tetroxide $\ce{N2O4}$ are not. I understand it is due to absorption of light when its ...
0
votes
1answer
1k views

pH of bleach solution slowly decreasing?

I work within a science department in a school. We are demonstrating Universal Indicator and something odd has happened. Our bleach solution (~2.5% Sodium hypochlorite) turns blue when UI is added but ...
10
votes
3answers
42k views

What is the difference between “molecular mass”, “average atomic mass” and “molar mass”?

I don't understand the difference between "molecular mass" and "average atomic mass". They seem like the same thing to me. Is it that average atomic mass is just the weighted average of the "weights"/...
1
vote
2answers
5k views

Is melting of Tar for road construction a reversible change?

In India roads are made up of a black liquid which is prepared by melting a black material(probably coal tar). After cooling the liquid becomes very rigid. Can this solid be converted back to its ...
3
votes
4answers
43k views

Difference between reversible and irreversible processes

On a quiz, I was asked for the difference between reversible and irreversible processes. I said: For a reversible process, you can change direction at any time without disturbing equilibrium. For an ...
5
votes
2answers
6k views

Why do triple bonds have a low NMR value?

Double bonds has a positive shift compared to single bonds. It seems like that there would be a trend but then the triple bond negatively shifts, despite having great electron density similar to the ...
2
votes
1answer
7k views

Calculating molecular weight of an acid based on titration data

If $\pu{2.600 g}$ of a weak diprotic acid were dissolved in $\pu{100 mL}$ of distilled water and a $\pu{10 mL}$ aliquot of this solution required $\mathrm{21.60\ mL}$ of $\mathrm{0.1000\ M\ NaOH}$ to ...
4
votes
1answer
2k views

How are subshells and shells arranged in an atom?

If $\mathrm{2s}$ and $\mathrm{2p}$ are in the second energy level, and $\mathrm{3s}$, $\mathrm{3p}$, and $\mathrm{3d}$ are in the next (3rd) energy level, how are these subshells arranged in space in ...
2
votes
2answers
299 views

Recovery and Disposal of Unknown Copper Compound

About a month ago, I ran a small electrolysis experiment in an old fish bowl with a $\ce{MgSO4}$ electrolyte and copper electrodes. It ran for about 3-4 hours. Now, a month later, I am left with ...
4
votes
1answer
3k views

Do all conversion factors have an infinite number of significant figures?

I believe conversion factors have an infinite number of significant figures. They should be exact values; but not all of them are, are they? I looked at a pdf document (via the Internet Archive) and ...
2
votes
0answers
79 views

Understanding the energy produced from oxidizing 1 kg of lithium

I am reading the following paper in preperation for a research project on the theoretical energy density of batteries: Lithium - Air Battery: Promise and Challenges and on the second page they ...
3
votes
1answer
1k views

Water extraction of ethanol from petrol

We have now 10% ethanol mixed petrol. Seller says that if this petrol comes in contact even 10 ml of water, all ethanol which is mixed in the petrol will be extracted by water, is it true?
2
votes
1answer
2k views

Reaction of Cu in hydrochloric acid bath with exposure to air over several months?

I assume that copper will be slowly oxidized by oxygen, dissolved in water, forming copper(I) oxide (as stated here): $$\ce{4 \overset{\pm0}{Cu} + O2 -> 2 \overset{+I}{Cu}_2O}$$ Reaction rate ...
1
vote
1answer
576 views

At what temperature will 6 grams of KMnO4 saturate 100 grams of water

I am trying to obtain more $\ce{KMnO4}$ from less amount by crystallization method. If I got the temperature I would easily make the desired amount. If I am choosing the wrong method, please tell me ...
2
votes
0answers
73 views

If a conductivity meter is calibrated with aqueous standards, can it be used to measure the conductivity of an organic-based solvent system?

Trying to figure out if the calibration solutions for a conductivity probe/meter must be of a similar nature to the system which will be measured. I can only find aqueous calibration solutions online, ...
1
vote
1answer
5k views

Separation of 2 compounds ( Powder )

Suppose I have a mixture of 2 pure binary compounds, a white powder. What is the best method to separate the 2 compounds? What I have thought of so far is to dissolve powder in DI water and carry ...
1
vote
0answers
372 views

QMOT | Orbital mixing in methyl

The following picture is from E. V. Anslyn Physical Organic Chemistry and shows constructing of MO of methyl using QMOT. MOs $\textbf{E'}$ and $\textbf{D'}$ are formed by mixing $\textbf{D}$ and $\...
1
vote
1answer
101 views

Enthalpy Change

If I mixed $25.0\ \mathrm{cm^3}$ of $0.350\ \mathrm{mol\space dm^{-3}}$ sodium hydroxide solution with $25.0\ \mathrm{cm^3}$ of $0.350\ \mathrm{mol \space dm^{-3}}$ hydrochloric acid. The temperature ...
1
vote
1answer
2k views

If you are given ΔH for this reaction which occurs at constant pressure, what additional information you need to determine ΔE?

Reaction: $\ce{2Al + 3Cl2 → 2AlCl3}$ Answer: We must have either temperature, or the values of P and ΔV in order to calculate ΔE from ΔΗ. Since ΔH is given, we can use the formula ΔE=ΔH-PΔV to ...
3
votes
2answers
1k views

What equipment to use to make liquid oxygen?

I'd like to do some experiments with liquid oxygen but as a first step I'll have to make some. Unfortunately I don't have any experience designing cryogenic experiments. I'm thinking I'll cool gaseous ...
1
vote
2answers
473 views

Calculate concentration gradients in FPLC

Our FPLC works with two solutions: A: 20 mM Tris.HCl, 0.2 M NaCl, pH 7.8 B: 20 mM Tris.HCl, 1.6 M NaCl, pH 7.8 I'm interested in sample volume from 102 mL to 117 mL. The FPLC will have a linear ...
2
votes
1answer
1k views

Can water volume reduce with introduction of another chemical [duplicate]

Can a chemical be introduced to a volume of water which can actually reduce the volume of water in that container?
0
votes
0answers
66 views

Hydrogen phase transition

A sample of hydrogen at a pressure of 7.10×10-2 atm and a temperature of 26.4 K is compressed at constant temperature to a pressure of 18.5 Which of the following are true? 1. One or more phase ...
-2
votes
2answers
555 views

Does calcium carbonate remove calcium from our bones? [closed]

Is it true that milk contains calcium carbonate which removes calcium from our bones so we shouldn't drink it?
6
votes
1answer
4k views

Carbonyl oxygen as nucleophile

Aldehydes and ketones have electrophilic centres at their carbonyl C, since the carbonyl O polarises the bond and attracts electron density towards itself on account of its high electronegativity. But ...
3
votes
1answer
1k views

Reaction of CaO with C

$\ce C$ is a good reducing agent and hence it can remove oxygen from $\ce{CaO}$. But instead of forming $\ce{Ca}$ and $\ce{CO}$, the products are $\ce{CaC2}$ and $\ce{CO}$. Why does this happen?
8
votes
1answer
6k views

Oxalate ion dentiticity - why is it bidentate and not tetradentate?

Why is the oxalate ion a bidentate ligand? Why does it not act like a tetradentate ligand (having four oxygen atoms, with lone pairs)?
0
votes
1answer
1k views

Bends in cis Isomers

It’s been said over and over in my biochemistry books that the cis-double bonds between the Cs in the hydrocarbon tails in triglycerides causes a kink. This kink disappears when the bond is isomerized ...
3
votes
1answer
24k views

How to determine force constant of C-C bond in ethanol?

How would one determine the theoretical force constant of the C-C bond in ethanol? We are asked to calculate the frequency of the C-C bond (theoretical), but to do this we need a force constant, which ...
0
votes
0answers
158 views

Bisulfate vs Bisulfite to neutralize off gassing in paint [duplicate]

I need to neutralize the off gassing in wall paint that contains one or more of the antimicrobial compounds of isothiazolinone, chloromethylisothiazolinone, methylisothiazolinone, benzisothiazolinone,...
3
votes
1answer
2k views

Hybrization of H in HNO [duplicate]

There is a problem that states: Find the molecular geometry of each molecule and the hybridization of each atom in the molecule. The two molecules are HNO and HCN. I found HNO to be sp3 hybridized and ...
0
votes
1answer
1k views

LiOH base ionization reaction

What is the base ionization reaction for LiOH? Usually, the reaction is like this: $$Base + \ce{H2O->H}[Base] + \ce{OH-} $$ But $\ce{LiOH2+}$ makes no sense. So what could the reaction be?
1
vote
0answers
454 views

Best Method To Make Large Graphene Oxide Sheets?

There are so many methods to make graphene oxide now, I'm not exactly experienced enough to know which is ideal. I want to know what the best method is for making large graphene oxide membranes. The ...
4
votes
1answer
139 views

Hill system with isotopologue

I'd like to use Hill notation (i.e. CH, then alphabetical), but I am not sure how to include isotopologues (i.e. carbon-13) in this notation. For example, what would be the preferred form of ...
7
votes
2answers
378 views

What does the “h” “k” and “(5.2.2.02,6)” mean in Dibenzo(h,k)-4-oxatricyclo(5.2.2.02,6)undec-8,10- diene-3, 5-dione

I am preparing to do an experiment that involves synthesizing Dibenzo(h,k)-4-oxatricyclo(5.2.2.02,6)undec-8,10- diene-3, 5-dione via a Diels-Alder reaction. Could someone please explain the ...
1
vote
0answers
51 views

Line of maximum density in liquids

Why is the thermal expansion coefficient zero along the line of maximum density in liquids? Why is $(∂^{2}V/∂T^{2})_{P} > 0$ along the same line?
1
vote
1answer
81 views

Solutions of several salts

What happens when you have a solution of a salt, and then try to dissolve another salt in that solution? I know about the common ion-effect etc, but how do you solve problems like this: How much AgCl ...
1
vote
1answer
688 views

Fractional Distillation

Why does the long length of the fractionating column in fractional distillation enable more effective separation of two liquids in a mixture? (basically what's the purpose of the fractionating ...
1
vote
0answers
192 views

What is the justification for Ligand Close Packing Model?

The LCP model predicts that nonbonded atom to atom distances remain approximately the same when the central atoms are changed. What is the theoretical justification for this? thanks
1
vote
2answers
4k views

Molarity is dependent on temperature?

Okay I know that as the temperature rises the number of particles in a given volume decreases. The molar volume likewise increases. So the number of molecules per liter would decrease as the ...
-2
votes
1answer
18k views

Calculate the mass of butane gas that would be needed to heat 724 cm³ of water from an initial temperature of 7.44 °C to 50.7 °C [duplicate]

The thermochemical equation for the combustion of butane is: $$\ce{2C4H10(g) + 13O2(g) -> 8CO2(g) + 10H2O(l)} , \quad\Delta H = -5748 \ \mathrm{kJ\cdot mol^{−1}}$$ So far, I've calculated the heat ...
0
votes
1answer
1k views

Calculate the amount of energy released when 500 cm³ of methane gas at STP reacts with excess air according to the equation:

$$\ce{CH4(g) + 2O2(g) -> CO2(g) + 2H2O(l)} \qquad \Delta H = -890\ \mathrm{kJ\ mol^{−1}}$$ I am not totally sure how to work this out. What I did, though, was: $\ce{CH4}$ $M = 16\ \mathrm{g/mol}$...
0
votes
1answer
20k views

Calculate water hardness from grams of CaCO3

We have to figure out what the water hardness in mg/L or ppm is for a $\pu{20ml}$ solution of $\pu{0.400M}$ $\ce{CaCl2}$. We learned that the formula for hardness is mg/L of calcium carbonate per ...
-1
votes
1answer
1k views

How to use the Nernst Equation

So I understand the Nernst Equation, but I don't have some info. (Please bear with me, I'm in secondary.) I'm doing a Cu - Al cell. My E cell is negative (-1.33). Does this have an affect on the ...
2
votes
1answer
89 views

Must compounds formed between solids be a solid as well?

My teacher gave us a long list of compounds and asked whether they are solid, liquid, or gas at room temperature and normal atmospheric pressure. I only know the more common compounds (eg. carbon ...

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