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# Tag Info

26

There is no true, accepted definition of heavy metal. I was taught to apply the option a metal that has density equal to or over $5.0\ \mathrm{g/cm^3}$. Other variants include a different density range, specific gravity over density, environmental impact, atomic number, toxicity, or atomic mass, even chemical properties. See here$^{[1]}$ for further ...

24

This is very hard to answer precisely, as there are many different carbon capture strategies, and economics at the scale required is quite different from our normal understanding. However, I'd love to see some attempts to at least get order of magnitude estimates, or sources with more in-depth analyses. Here is an implementation of carbon capture and ...

22

You're dealing with a mixture of similar hydrated salts instead of a single salt (as in the example of $\ce{Ca(NO3)2}$). The notation $\ce{K2O-nSiO2-xH2O}$ means that there are different crystals with varying proportions of silicon dioxide and water (hydration). i.e. $n$ could be $1$, or $2$, $3$, etc. and $x$ likewise, for any given molecular "speck". A ...

11

There is no set criteria, as far as I am aware. I tend to think of iron as the median. Thus, I would happily refer to metals above iron as being 'heavy', i.e. density in excess of $\pu{7.8 g cm-3}$.

10

With reference to the discussion in the question comments, this product does not appear to appreciably reduce carbon emissions in total. It does however appear to reduce carbon monoxide emissions. As carbon monoxide is a product of incomplete combustion, it is plausible that the additive is helping the fuel burn more completely. Broadly speaking, you would ...

10

Pentane, hexane, heptane, and octane are labelled with the ‘environment’ hazard pictogram (GHS09) since they are considered toxic or very toxic to aquatic life with long-lasting effects (H411 or H410) because of their toxicity to the water flea Daphnia magna in standardized tests. Nevertheless, nonane is not completely harmless; it still may cause long-...

10

While gravity does cause some separation of atmospheric constituents at high altitudes, the reason why ozone doesn't migrate to the ground has more to do with its chemistry. Ozone is pretty unstable and is formed from some chemical reactions and from the interaction of oxygen with UV light. But it is unstable and decays fairly quickly. This means that is ...

9

Though I've never heard of that statement before, it's possible that nitrogen oxides formed by electrostatic discharge (not only lightning, but even glow discharge) dissolve in the rainwater, producing nitrous and nitric acids. There is a 1997 citation describing comparison of pH in rain accompanied (or not) by lightning. That said, presence of fly-ash ...

8

It's... feasible. There are a number of technologies that are being considered. Costs will be high, some number of billions or trillions: you're talking planetary engineering, here. The most obvious option is to plant trees. The obvious problem with that is that even planting them at the same speed as they are being removed is infeasible. Unfortunately ...

8

In a rainwater tank in contact with air, dissolved iron is probably oxidized to iron(III) ($\ce{Fe^3+}$). A simple and sensitive test for $\ce{Fe^3+}$ in water uses thiocyanate ions ($\ce{SCN-}$, also known as rhodanide), which form the blood-red coloured complexes $\ce{[Fe(SCN)(H2O)5]^2+}$, $\ce{[Fe(SCN)2(H2O)4]+}$, and $\ce{[Fe(SCN)3(H2O)3]}$. $$\ce{[Fe(... 7 "Give me a half a tanker of iron and I will give you another ice age" That's the claim of people who believe in iron seeding the ocean. The link claims that "the addition of silicic acid or choosing the proper location could, at least theoretically, eliminate and exceed all man-made CO2", but no citation is given. As to cost? "Current estimates of the ... 7 First we have to look how the greenhouse effect works for all gases: Light with a wavelength not absorbed by the atmosphere gets absorbed by the soil and heats up the earth. Because of black body radiation for 300K the earth starts to emit light itself with a maximum in the IR spectrum. Light with this frequency gets readily absorbed by vibrational ... 7 This pretty much what happens (among other processes) in a three-way catalyst of a car:$$\ce{2CO + 2 NO ->[\mathrm{cat}] 2CO2 +N2}$$5 That is a good rule of thumb. It is based on the Arrhenius equation$$k = A {\operatorname{e}^{\frac{-{E_{\text{act}}}}{RT}}} You'll find that the "temperature doubles every 10 degrees" rule only applies if the following assumptions are valid The reaction must obey the Arrhenius equation it must have an entropic pre-term based on collision probability ...

5

As you state, aromatic compounds such as benzene, naphthalene, xylene and toluene have noticeable odor (ergo "aromatic"). In addition, odorous oganosulfur compounds may remain, though in Europe and North America effort is made to remove them (kerosene and heating oils may have higher amounts of oganosulfur contaminants). In the US, Methyl tert-butyl ether (...

5

At first thought, it might seem that rainwater should be clean like distilled water, as it evaporated, condensed, then fell back to earth. It sounds like a condenser or distillation apparatus in a laboratory. But in reality, the process is very different. To start with, every raindrop must have a particle to condense upon, called a cloud condensation ...

4

The problem with carbon capture is not so much that we lack the technology to do it, it's more that we lack the technology to do it in a way that is economically feasible. Take your example - according to the US Energy Information Adminstration, it takes about 1.09 lbs of coal to generate 1 kWh of electricity. A typical coal-fired plant might produce an ...

4

This is probably a more complex problem than your instructor intended. In addition to the various metals having different toxicities, different compounds of these metals have different toxicities. For example, nickel metal has low toxicity, but the compound $\ce{Ni(CO)4}$ is a poisonous, flammable, volatile liquid. Likewise alkyl mercury compounds, e.g. $... 4 If you want to test for the presence of iron(II) in solution, you could add$\ce{CO3^{2-}}$ions to form a green precipitate. This could be extracted and measured, although it could be a very small amount unless you concentrated the sample water by evaporating it down. The main tool would be an accurate balance, but also some liquid measuring equipment. ... 4 According to Introduction to Atmospheric Chemistry, by Daniel J. Jacob, Princeton University Press, 1999,Chapter 10, An important component of aircraft exhaust is nitric oxide ($\ce{NO}$) formed by oxidation of atmospheric$\ce{N2}$at the high temperatures of the aircraft engine. In the stratosphere$\ce{NO}$reacts rapidly with$\ce{O3}$to produce$\...

4

Water issues tend to be very specific to a certain location, so it is not possible to say exactly for sure what is happening in your situation. Pure water has no taste. The taste comes from the impurities. Impurities, which are almost always present, can partially be removed by the filter shown. That filter looks like a carbon filter which is effective ...

4

According to this abstract$\mathrm{^{[1]}}$, both aerobic and anaerobic processes play a role in the natural degradation of PCB's. Studies have identified two distinct biological processes capable of biotransforming polychlorinated biphenyls (PCBs): aerobic oxidative processes and anaerobic reductive processes. It is now known that these two ...

4

An easy step-up from vinegar would be hydrochloric acid, $\ce{HCl}$. It's known as muriatic acid and is sold in bulk at pool-supply and home-improvement stores. The concentration from such sources is typically ~8.9M, or 32% (by mass). Such is what I measured from home; it's typically advertised as 30%-32%. There are rumors (which I haven't been able to ...

3

I suggest to stay with commercially available, read-made solutions. These products are thoroughly tested and certified. They typically contain around 5% of various benzalkonium chlorides, such as N-Myristyl-N-benzyl-N,N-dimethylammonium chloride, as biocides. UPDATE As far as the mildew is concerned: The orange ladybird (16 white spots) and the 22-spot ...

3

This question is impossible to answer without knowing which TPE you mean - TPE is a mixture of thermoplastic elastomers, which is a huge class of compounds. PVC is polyvinylchloride, which is a specific compound. I found an MSDS here: http://www.fishersci.com/ecomm/servlet/msdsproxy?productName=AC183320010&productDescription=POLY My advice is to ...

3

Although it is true that soil $\mathrm{pH}$ plays a role in the color of hydrangeas, the presence of aluminium is actually what determines the flower color. Aluminium is a naturally occurring mineral that is found in most soils, however, just because a mineral is in the soil doesn’t mean the plant is absorbing this mineral. This is where soil $\mathrm{pH}$ ...

3

The numbering clearly is not a part of the international GHS (Globally Harmonized System of Classification and Labelling of Chemicals) labeling scheme. On a side note, GHS requires hazard pictograms, coded hazard statements (Hnnn and EUHnnn) coded precautionary statements (Pnnn) but typically does not give any information on the how/where to dispose ...

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