# All Questions

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### 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?
2k views

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

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 ...
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 ...
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 ...
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 ...
8k views

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 ...
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 ...
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 ...
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 ...