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1answer
3k views

Block on the Periodic Table?

What are the blocks of the periodic table? What is the purpose of naming the elements per block group? What do they signify?
6
votes
1answer
2k views

How to calculate the potential via Hess's law? Is my textbook wrong about this?

Given the two reduction half-reactions for the following fuel cell, determine the standard cell potential $E^\circ_\mathrm{cell}$, $$\ce{CH4 (g) + 2 O2 (g) + 2 OH- (aq) -> CO3^2- (aq) + 3 H2O}.$$ ...
1
vote
1answer
962 views

Information depth in x-ray photoelectron spectroscopy (XPS)

What is 'information depth' in XPS and what does determine it? Also how does it depend on the 'take-off angle'?
1
vote
1answer
93 views

Can I use harvested plants to gain electric power?

I was just thinking - plants are mostly acid. Even grass is quite acid. Could you create battery cell from squashed plants (after cutting them in pieces)? How much effective would it be? Could you ...
2
votes
1answer
2k views

What copper oxide is being created upon electrolysis?

Whenever using copper as anode, I end up with cyan dust that doesn't dissolve in water. What's that (presumably) oxide? Is it poisonous? Can I dissolve it in something to perform electroplating with ...
10
votes
1answer
4k views

What allows sulfur and phosphorus to expand their octet?

There are many compounds in which the stability of a molecule is not governed by the presence of octet configuration in central atom. In most of the cases the central atom is generally sulfur or ...
0
votes
1answer
2k views

Relationship between Van der Waals forces and the boiling point

Choose the right answers in the following statement: The boiling point of a liquid substance is higher as the Van der Waals forces (in/between) the molecules of the substance are (lower/higher). I ...
3
votes
1answer
1k views

What's the difference between Carvacrol and Thymol?

What is the difference when it comes to separating Carvacrol and Thymol on HPPLC with reverse phase - C18 column? Carvacrol elutes first, is that because it is ortho?
0
votes
2answers
282 views

How to calculate the concentrations of the species in the carbonate equilibrium from a titration with hydrochloric acid? [closed]

Lake water contains dissolved sodium carbonate and sodium hydrogen carbonate. The following equilibrium exists: \begin{align} \ce{HCO3- &<=> H+ + CO3^{2-}}& \frac{\ce{[CO3^{2-}]}}{\ce{...
3
votes
1answer
1k views

Recrystallization of two unknown compounds?

I managed to separate a binary mixture(in solid form) of two unknown substances into two individual solid compounds. For the separation, I used an acid-base extraction with dichloromethane, NaOH, and ...
1
vote
2answers
73 views

Adding concentrations to obtain mass

I have a question that gives two concentrations and asks for the mass of HCl formed by the reaction. I have two concentrations: 250mL of 4.00M $\ce{H2SO4}$, and 250mL of 1.00M $\ce{NaCl}$. Here is ...
4
votes
1answer
13k views

How is chlorophyll made in plants?

I've been studying photosynthesis and something made me think about how chlorophyll itself is made in plants.How exactly is it formed ?
1
vote
2answers
668 views

Binary Molecular Compounds of Nonmetals

How does one determine the formula for two non metal elements? Such as Nitrogen and Oxygen. I look at the charges with Nitrogen having -3 and Oxygen having -2. How would I get to zero? How do you ...
1
vote
1answer
110 views

How can I determine/quantify the presence of boron nitride on a metal surface?

We use micron-grade hexagonal boron nitride (hBN) to coat the surface of bullets that are jacketed in gilding metal. This coating is mechanically embedded/plated onto the surface in order to increase ...
3
votes
1answer
20k views

Mechanism for the Beilstein test?

What is a possible mechanism for the Beilstein test for halogens ? I can't seem to find a arrow pushing mechanism for this reaction.
10
votes
3answers
52k views

Mechanism for reaction of Tollens' reagent with aldehydes

Upon treatment with Tollens' reagent (ammoniacal silver(I) nitrate), aldehydes are oxidised to carboxylic acid, and silver(I) is reduced to silver metal. I am trying to find a mechanism for the this ...
1
vote
1answer
2k views

Making a solution with two solutes

I need to make a solution that has a 15% (wt/wt%) HCl acid concentration and a 6% (wt/wt%) NaI concentration. I'm not sure yet how much of this solution I will be required to make so a general recipie ...
10
votes
3answers
38k views

Water flow in condenser

How should the water flow in your condenser? From the flask to the top of the condenser, or from the top of the condenser back to the flask? I could imagine both: flask to top will fill the entire ...
4
votes
1answer
2k views

Something denser than lead but with lead like properties?

I read that tungsten is 1.8 times more dense than lead. What other elements are denser than lead but safe to handle. I want something that will fit under the keys of my computer keyboard so my pinky ...
21
votes
2answers
42k views

How does a lone pair of a central atom affect the dipole moment?

Dipole moment is the degree of polarity, i.e. the seperation of positive and negative charges. But I am not getting the intuition why and how lone pairs affect the polarity and dipole moment. I cannot ...
2
votes
1answer
3k views

Reduction potential and electron affinity

Why is it that fluorine has a much greater reduction potential than chlorine, despite the fact fluorine has a lower electron affinity than chlorine? I understand that fluorine has a lower electron ...
1
vote
1answer
3k views

Can I perform electroplating with sodium carbonate and copper?

I want to avoid anything poisonous during electroplating. I can't avoid copper oxide though. I have dissolved $\ce{Na2CO3}$ in water and I'm trying to electroplate aluminium with copper: As you can ...
1
vote
2answers
8k views

Can I use sodium hydroxide (NaOH) to remove oxides from metals? [closed]

Sodium hydroxide dissolved in water is a very strong base. I think this could mean it could de-oxidate the metal oxides during re-ox reaction. Basically, I ask whether the following happens: $$\ce{...
1
vote
1answer
1k views

Determine the concentration of the original NaOH solution

This was a question on the mt exam two days ago : A chemist added 40.0 mL of an $NaOH$ solution to 90.0 mL of 0.400 M $HCl$. The solution was then treated with an excess of $\text {nickel(II) ...
6
votes
1answer
4k views

Rusting of an Iron nail at oil water boundary surface

Recently at school, I did some experiments on corrosion. Everything mostly went as expected, but the result in one of the test was quite baffling. This test had an iron nail in water with some of ...
4
votes
1answer
124 views

Fermentation in beer (reaction schemes)?

I've been struggling with this for a while, and I can't seem to solve the problem. Alcohol is made in the fermentation process in beer: Sugars formed during mashing (maltose and maltotriose) will ...
0
votes
1answer
2k views

How exactly do you measure the free energy of a reaction?

It is to my understanding that ΔG can be positive or negative given whether the reactant is exothermic or endothermic. How would you go about measuring the energy (in joules) of a reaction using the ...
8
votes
2answers
4k views

Can lead(II) oxidize tin metal in aqueous solution?

According to my textbook, element $\ce{X}$ can oxidize element $\ce{Y}$ if $\ce{X}$ was lower in the activity series. Lead is lower than Tin in the activity series table in the textbook, but the ...
0
votes
2answers
4k views

How to determine amount of CO₂ in soda water

I've got a problem in determining the amount of $\ce{CO2}$ in soda water. Basically, I have boiled some purified water to remove the dissolved gas. By using a SodaStream machine, I made carbonated ...
1
vote
1answer
263 views

How can we calculate enthalpy change in a closed tank containing methanol adsorbed by activated carbon?

Here's the problem in the simplest way: I have a closed box containing methanol adsorbed by activated carbon. The box is made from copper. A pipe is connected to that box, which has condenser on the ...
10
votes
4answers
4k views

Which electrodes do not corrode at all?

I had used spare pieces of metal to perform electrolysis. They all had the disadvantage that they corrode when used as anode - and some of the oxides are toxic (copper, chromium). I've found that ...
1
vote
1answer
3k views

Does washing soda (sodium carbonate) turn into baking soda (sodium bicarbonate) over time?

I have some sodium carbonate. But it's over 20 years old and was not kept in tight bottle. I wonder if this compound absorbs $\ce{H2O}$ and $\ce{CO2}$ from air. I guess I'd need to burn it a little ...
4
votes
3answers
5k views

Can I perform electrolysis without electrolyte? (with distilled water)

When performing electrolysis at home, I usually used salt water as electrolyte. The problem is, that this method also produces chlorine and chlorine is aggressive to both humans and electrical ...
0
votes
1answer
56 views

Loading nickel metal hydride battery for the first time

I just bought a new hair clipper and I was about to start shaving my head when I noticed that it was almost at 0%. It has a nickel metal hydride battery. The manual says I have to load it for 24h ...
1
vote
2answers
127 views

How is it thermodynamically possible to obtain energy from a piece of coal?

If we put a piece of coal in open air we don't get any energy of it. But if we put fire to it in open air we get energy. Explain it with help of Gibbs free energy.
7
votes
2answers
3k views

How does neutralization of free radicals by $\beta$-carotene work?

In my understanding, by bonding to the free radical species, say by one of the double bonds, a new free radical on the $\beta$-carotene develops.
11
votes
4answers
66k views

Is sulfuric acid or hydrochloric acid stronger?

Of my belief, sulfuric acid might be a little stronger than hydrochloric acid. Because even though they both are strong acids, one mole of sulfuric acid produces two times as much $\ce{H+}$ as one ...
2
votes
2answers
19k views

Basic chemistry of the Shinoda test for flavonoids?

In this test, four pieces of magnesium fillings (ribbon) are added to the ethanolic extract followed by a few drops of concentrated hydrochloric acid. A reddish colour indicates the presence of ...
4
votes
0answers
100 views

Synthesizing monodisperse PbS quantum dots

For a research project, I am trying to synthesize lead (II) sulfide quantum dots using the method of Li et al.. I am injecting sulfur dissolved in 1-octadecene into a mixture of $\ce{PbO}$, oleic ...
0
votes
3answers
4k views

Can redox reactions involve only non metals?

When non metal react they form molecule, and whether the bond is polar or not, the elements in the molecular compound will not have charges what so ever, because they are not ionic. But can non metals ...
1
vote
1answer
148 views

When will peroxide form?

A very typical example of a compound of peroxide is $\ce{H2O2}$. When like the title says, will such compounds form, despite usually oxygen will have a oxidation number of 2-?
0
votes
2answers
228 views

How can I find out the concentration of chlorine in an acid bath?

A professor I have gave the class this question, can anyone help? This is the first part of the question. (Also, my professor is from Bangladesh...so yea...) It's the year 2395, and the world is in ...
0
votes
2answers
3k views

Transition metal order of filling electron

There is a specific order for filling electron for transition metals, but I don't know if it applies to other elements too? Some thing to take note of in this picture is the order of 3d and 4s. My ...
2
votes
1answer
5k views

Calculating the electronegativity of an element from bond dissociation energies

Calculate the electronegativity of fluorine from the following data: $$\begin{align} \text{BDE}(\ce{H-H}) &= \pu{104.2 kcal/mol} \\ \text{BDE}(\ce{F-F}) &= \pu{36.6 kcal/mol} \\ \text{...
3
votes
1answer
951 views

How to determine the molecular formula of a compound given its molecular mass and mass percentage contribution of the involved elements?

Hydralazine is a drug used to treat heart disease. It is $59.99\%$ carbon, $5.03\%$ hydrogen, and $34.98\%$ nitrogen and has a molecular mass of $160.178$. What is the molecular formula for ...
5
votes
1answer
16k views

How is the charge of covalently bonded atoms determined?

My question is about what it is - at the subatomic level - that determines the charge on atoms which participate in covalent bonding in reality. I understand that formal charge is just that - it's a ...
1
vote
0answers
30 views

Simulating enzymatic change rates of Carbonic anhydrase

I'm trying to simulate effects of carbonic anhydrase on cellular pH as caused by changes in bicarbonate. I assume a bicarbonate homeostatic mechanisms which replenishes intracellular concentrations ...
10
votes
3answers
18k views

Why is standard reduction potential an intensive property?

My book says that Since the number of electrons lost must equal the number gained, the half-reactions must be multiplied by integers as necessary to achieve the balanced equation. However, the ...
4
votes
3answers
840 views

Refluxing with tilted condenser

Can you reflux without any problems/dangers with a tilted condenser (e.g. because you don't have enough space in your fumehood)? I would say there isn't a problem, because both the surface area of the ...
1
vote
1answer
7k views

Why does acetyl have negative charge?

"Acetylation (adding an acetyl group) and phosphorylation (adding a phosphate group) make the histones more negatively charged because acetyl and phosphoryl groups are negative. They are "glass is ...

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