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7
votes
2answers
6k views

Which theta should be taken from x-ray diffraction pattern for calculating Scherrer's equation?

We use Scherrer's equation to calculate crystalline size of a particle: $$d = \frac{Bλ}{β\cos{θ}}$$ But which theta should we take from the XRD pattern for this calculation? For example, the ...
10
votes
4answers
16k views

Maximum temperature attainable by thermite reaction

In the thermite reaction $$\ce{2Al(s) + Fe2O3(s) -> 2Fe(l) + Al2O3(s)}$$ what is the maximum temperature attainable by the products? Assume reactants at $25\ \mathrm{^\circ C}$ and $1\ \mathrm{...
6
votes
1answer
9k views

How can scientists be certain that there are no undiscovered elements missing from the periodic table from hydrogen to lawrencium?

Scientists are certain that there are no undiscovered elements missing from the periodic table from hydrogen to lawrencium. How? and why?
12
votes
1answer
761 views

What are the key chemical characteristics that determine the octane rating of fuel?

The octane rating of petrol (gasoline) is a measure of the how much compression a fuel air mixture can have before detonating (which in petrol engines is a bad thing as you want the mix to combust ...
8
votes
1answer
7k views

Is an explosion merely an exothermic reaction?

An exothermic reaction is apparently one that releases energy to it's environment. According to Wikipedia, an explosion is a rapid increase in volume & energy. Does this mean that an explosion is ...
8
votes
4answers
3k views

Is there a standard symbol for molar density?

Is there a standard symbol for molar density, i.e. $n/V$, where $n$ is the total number of moles of every species in a system? I realise that there is standard term "molar volume", which is the ...
12
votes
2answers
4k views

What is the opposite of a surfactant?

Surfactants decrease surface tension between two fluids. What do you call a substance that increases the surface tension between two fluids? How is this effect acheived?
7
votes
1answer
3k views

What is the product formed in the reaction of dimedone and benzaldehyde?

I'm having a hard time deducing the structure of the product formed when dimedone and benzaldehyde react in the presence of catalytic piperidine. I think that a Knoevenagel reaction will get me to ...
3
votes
1answer
8k views

What is the difference between saturated and unsaturated fatty acids?

Chemically speaking, what are the biggest differences between saturated fatty acids and unsaturated fatty acids? What are the effects of those differences on the geometry of the molecule? And what is ...
5
votes
3answers
1k views

Is there a household method to decolorize potentially contaminated water?

I am living in my dorms at the moment and apparently it is an accepted thing that the water in the building is brown and yellow. According to my RA, this is a characteristic of the town I live in. ...
1
vote
1answer
1k views

Determining enthalpy and internal energy of formation for potassium superoxide

Given $2.14\ \mathrm g$ of $\ce{K(s)}$, determine $\Delta H^\circ_\mathrm{f,m}$ and $\Delta U^\circ_\mathrm{f,m}$ for $\ce{K2O}$. We know: The calorimeter's constant: $1849\ \mathrm{J\...
3
votes
2answers
317 views

Is alkene reaction with hydrogen to form an alkane an addition reaction?

I have seen in some textbooks that such a reaction is listed under reduction of alkenes. I understand that the double bond is getting reduced to single bond and one hydrogen atom is added to each of ...
5
votes
1answer
214 views

Thought Experiment: Applying a high frequency high voltage to methane

I am in the process of constructing a kitchen waste digester (vegetable/fruits) from which, hopefully, over time adequate methane may be collected to burn. The digester won't be complete for several ...
6
votes
2answers
2k views

What chemical compounds were used in CRT phosphors?

In the old days computer monitors and televisions were built from cathode ray tubes (CRTs) where the image was generated by an electron beam hitting phosphors which emitted light approximating the ...
14
votes
1answer
824 views

Why do some materials turn black and others white after combustion?

Most solids objects turn black after they are burnt. But some turn white. Why is that ?
10
votes
1answer
19k views

Why do single, double and triple bonds repel each other equal amounts?

I'm here to share with you something that totally confuses me, as I can't see the logic behind it, and my teacher doesn't know either. Let's take a set of bonds that's trigonal pyramidal, with a lone ...
4
votes
0answers
48 views

Compounds that vary water's superheated and supercritical limits [closed]

Are there any compounds that reduce water's sensitivity to extreme heat change and/or volatility to high heat (over 800 degrees Fahrenheit), whether organic or inorganic?
8
votes
1answer
1k views

Fitting titration curve

To simulate the action of gastric $\ce{HCl}$, we have titrated 100 ml of a meal with 0.1 N $\ce{HCl}$. To plot the data, use (R-code) ...
5
votes
1answer
589 views

Find mass of CO₂ and heat released per minute in a combustion reaction

I am not sure where to start with this problem. I know that $\small q = mc(T_f-T_i)$, but that seems like it would not help here. I think I need to balance the equation, but I am not sure how the rate ...
9
votes
1answer
950 views

What do graphene "armchair(5,5)" and "zigzag(5,0)" refer to?

I am reading some articles about the electronic properties of graphene and while reading it I came across graphene armchair and zigzag structures, which have different bond structures. The two ...
4
votes
3answers
16k views

Which has one monochlorination possibility?

Which would have one monochlorination possibility? 2,2-dimethylpropane: or 2-methylpropane: It seems I'm missing something because I thought both would only have one monochlorination possibility. ...
14
votes
7answers
4k views

Is there a simple field test for heavy water?

Thought experiment Given two glasses of water, how would one detect which glass contains heavy water, and which contains potable water without using complicated laboratory equipment? Something like ...
11
votes
3answers
23k views

What is the meaning of '(en)'?

What is the meaning of $\ce{(en)}$ on this two coordination compounds: $\ce{[Co(en)_2(NO_2)_2]Cl}$ $\ce{[Cd(en)_2(CN)_2]}$ Is it a type of compound? If yes, what is the meaning?
9
votes
2answers
2k views

How to fluorinate polyethylene?

I seek to put a layer of fluorine on a rotationally molded cross-linked polyethylene (XPE) plastic gasoline tank. I sell tanks and they will be more eco-friendly if I can accomplish this. I am an ...
7
votes
1answer
1k views

What sort of molecules or polymers are used in OLED displays?

OLED displays have been emerging as competitors for LCD displays for some time and are now common in mobile phones (see comparison of a Google Nexus 1 and an iPhone here) The displays use small ...
3
votes
1answer
725 views

What would happen to a Water/Lard Mix under pressure and high heat?

If water is mixed with lard oil and heated (creating some super-critical water), how does this affect the volatility of the mixture in comparison if it is a pure mix of either water, or lard oil? ...
17
votes
1answer
655 views

What is the chemistry behind this "petrol from air" technology?

A recent news report in the UK claimed a breakthrough in making a petrol equivalent from carbon dioxide and water: A small British company has produced the first "petrol from air" using a ...
1
vote
3answers
6k views

Looking for a safe exothermic reaction [closed]

Is there an exothermic reaction which produces 1 to 2 minutes of heat at around 175 degrees Fahrenheit, no toxic gasses and is considered to be more or less safe?
6
votes
1answer
4k views

What is the exact definition of Salinity?

I am a bit unclear on the definition of salinity. I have always thought of it as simply total dissolved ions. Wikipedia seems to agree "saltiness or dissolved salt content" but many other sources ...
10
votes
2answers
2k views

Why is tin(II) fluoride more effective in turning apatite into fluorapatite?

In more powerful toothpastes, like Crest Pro-Health, stannous fluoride is used in place of sodium fluoride. According to Wikipedia: Stannous fluoride converts the calcium mineral apatite into ...
2
votes
1answer
458 views

How does simulation software work at a fundamental level?

There are lots of software packages like Schr­­­ödinger Maestro or Argus Lab, which are used for simulations of docking. I have always been fascinated as to how such software works. What is the ...
3
votes
1answer
4k views

How to calculate the solubility of CaF2 at different temperatures?

At $\pu{25^\circ C}$ I used the free energy table for $G$ for the reaction and got $K_\mathrm{sp}= 10^{-9.02}$. I now need to find out what the solubility is at $10$, $20$ and $\pu{30^\circ C}$. ...
1
vote
1answer
3k views

Should I use specific heat to calculate how much fuel is required?

Question: A backpacker wants to carry enough fuel to heat $\pu{3.0 kg}$ of water from $\pu{20 ^\circ C}$ to $\pu{100.0 ^\circ C}$. If the fuel he carries produces $\pu{36 kJ}$ of heat per gram when ...
25
votes
5answers
1k views

Why are smoke odors persistent in fabrics?

Obviously smoke is very complex, but apparently phenol compounds are the main components of wood smoke that produce the characteristic odor. (One of more significant of these compounds seems to be ...
4
votes
1answer
2k views

Which C-C bond would break first, the one in ethane, or 2,2-dimethylpropane?

I have drawn the figures and determined intuitively that the larger molecule's $\ce{C-C}$ would break first. I made this assumption that ethane has the stronger $\ce{C-C}$ bond and I am correct, ...
5
votes
2answers
2k views

If a sugar is nonreducing, does that mean it doesn't ionize in water?

I'm thinking of sucrose, which I learned is nonreducing, what I take to mean it doesn't accept/take electrons from the surrounding solution. Does this also mean that it doesn't ionize and thus has a ...
2
votes
1answer
89 views

Mechanism of oxidation by dichlorotriazenetrione

How does dichlorotriazenetrione supply chlorine to a swimming pool and how does it oxidize organic material?
3
votes
1answer
617 views

Breakdown of valine

What are the chemical reactions responsible for the breakdown of valine in the body? I know oxidative deamination is part of the process but how is valine further broken down from an keto acid to ...
5
votes
1answer
1k views

The effect of structure on the boiling points of organic molecules

Why do molecules like methoxyethane, ethoxyethane and so on have lower boiling points than isomeric alcohols? I think it has something to do with the structure, but I don't exactly know what it is.
2
votes
2answers
10k views

If gases turn into liquids under pressure, what does carbon dioxide turn into?

Since there is no liquid state of carbon dioxide, what will carbon dioxide turn into when exposed to high pressure?
0
votes
1answer
104 views

Acid-base reaction is screwing up my synthesis

I'm gonna get kicked all the way to the Moon, but whatever. I am doing some nitroglycerin. I know the process, since the reaction itself is pretty basic. I know that it is an electrophilic ...
2
votes
0answers
116 views

Why does the passivation layer in DRIE protect just the mask and not the substrate?

Here's a good link as an introduction to DRIE: BSAC: DRIE Process Development The $\ce{C4F8}$ (refer Pg. 9 on the link) passivates the entire top layer. But when $\ce{SF6}$ ion bombardment occurs, ...
3
votes
2answers
23k views

Why is dialysis tubing impermeable to sucrose when it should retain >12,000 Da?

While writing up a lab for biology, I realized that the dialysis tubing for sale online seemed to retain large molecules (12-14,000 Da) but didn't specify an upper bound. I learned that the tubing is ...
12
votes
3answers
16k views

Cleaning a round-bottom flask, especially after distillation

I was wondering, how can I clean my RBF after doing a distillation? Cleaning it with a simple pipe-cleaner or similar cleaner is a headache, due to the roundness of the flask. Is there a more ...
3
votes
1answer
102 views

How do surfactants spread in the case of multiple materials?

For example, consider a pot of water with a drop of oil floating on it, with surfactants present in the water. Will the surfactants in the water spread evenly across all three interfaces (water/metal,...
9
votes
1answer
1k views

Why is bread warm at room temperature?

If I buy a loaf of freshly-made bread and leave it out at room temperature for a day or two, when I reach into the bag the air inside is much warmer than the rest of the room. Why?
4
votes
2answers
3k views

Can we separate positive ions from negative ions in a solution?

Can we make a solution containing only positive ions by using electrodialysis but instead of using 2 kinds of membrane (one blocks the positive ions and one blocks the negative ions) we can use only ...
6
votes
2answers
4k views

What's the energy density of liquid nitrogen?

Liquid nitrogen seems to be attracting a bit of attention at the moment as a medium of energy storage, both for electricity grid applications and for transport. For example, Highview (via the Internet ...
4
votes
1answer
2k views

Is this the correct relative Brønsted acidity in these four acids?

We are asked to sort these four acids by increasing Brønsted acidity: The problem is, I am confused why $\ce{H2F+}$ is the strongest acid of them all. I understand that stronger acids will have ...
7
votes
1answer
327 views

How can I determine the pH of solution?

Could anyone tell me how I would go about calculating the pH of 100.0 mL of 0.100 M $\ce{H2NNH2}$ ($K_\text{b} = 3.0 \times 10^{-6}$). Furthermore, how would this pH change when 20.0 mL of 0.200 M $\...

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