How do calcium carbonate and acid react

1371
Q: Subject: Calcium oxide as a fertilizer?

My son's chemistry teacher gave the following written assignment:

"In the spring, many farmers in the Main Valley sprinkle burnt lime = calcium oxide (s) on their fields. Farmers on the Jura plateau do not need this. Explain the meaning of this behavior using a reaction equation in brackets!"

Please help me to improve my knowledge of chemistry in this regard!


A: Of course, quicklime is not a fertilizer. It acts as a relatively strong alkaline substance against soil acidification. Keyword: neutralization and buffering. Let me take the example of sulfuric acid from acid rain.

CaO (s) + H2SO4 (fl) ———> CaSO4 (s) + H2O (fl)

Calcium sulphate (containing water: gypsum) reacts neutrally.

The soils of the Jura plateaus (e.g. in the Franconian Jura, in the Jura of Switzerland or on the Swabian Alb) consist of limestone, i.e. calcium carbonate.

If your son is a beginner, he can put it this way: Limestone and sulfuric acid react with each other. The limestone is broken down in the process; plaster of paris and carbon dioxide are produced.

CaCO3 (s) + H2SO4 (fl) ———> CaSO4 (s) + H2O (fl) + CO2 (G)

So here the limestone acts as the acidic buffering substance.

Otherwise, however, this is a complicated reaction. The limestone reacts alkaline with water from the outset. (You can test that with pH paper.) Behind this is the following equilibrium.

CaCO3 (s) + H2O (fl) <———> Approx2+ (aq) + HCO3- (aq) + OH- (aq)

This equilibrium system reacts with sulfuric acid - but ultimately with the same result as above.


1372
Q: I have read that volcanoes are formed where tectonic plates meet, among other things. Under the resulting pressure, the rock should heat up to such an extent that it melts.
That can't be true, because liquids require more volume than solids (apart from water).


A: Your objection is correct.

The heat development is correct. In addition, however, the rock can only melt if the pressure is right. A comparison is obvious: If you heat water, you can control its boiling point by changing the pressure (-> tip of the month). At high pressure there is no boiling; at lower pressure, the boiling point can even be below 100 C.

The continental floes press against each other; so the pressure is too high to liquefy the rocks. If a clod breaks somewhere, the pressure is relieved and liquid rock can escape as magma or lava. That is why volcanism is often associated with earthquakes.

This also applies to the hot spots, e.g. B. under Hawaii or under Iceland. It's glowing hot in the earth's mantle, but it is rather solid - well let's say highly viscous. Its density is even significantly higher than that of the earth's crust above. When the hot material penetrates the earth's crust, the pressure decreases and a volcano erupts.

Incidentally, the central NiFe core of the earth is also solid; it probably consists of metal octahedra, which can be deduced from the structure of the metal meteorites.

If the inner earth is solid, how can mineral pools form? The ions are easy to move because of the heat. At first they migrate around diffusely, but then increasingly collect with the formation of corresponding chemical compounds. Here the driving force is the chemical potential, which reaches a minimum when the connection is formed.


1373
Q: Subject: Questions about chemistry about soda and detergents, please read. THANKS!!!

we are two unsuspecting chemistry protocol writers and we have an urgent question about our protocols, which we hope you will answer.
How can you tell that a detergent contains soda? We have added hydrochloric acid to various detergents and observed them.

As an observation, we were able to determine that the following detergents Persil Megapearls, Ariel Compact heavy duty detergent, Ariel Compact mild detergent, heavy duty detergent (old), IMI and Spee Compact formed bubbles and foam. the Ariel Compact mild detergent and the heavy duty detergent (old) solidified again after a short time. now we don't know how to tell which detergents soda is in ?!


A: The hydrochloric acid breaks down soda. This releases gaseous carbon dioxide:

N / A2CO3 + 2 HCl ———> 2 NaCl + H2O + CO2

Another sign of the presence of soda: The solution or slurry of washing powder has an alkaline reaction. You can check that with an indicator paper.


1374
Q: I read in a book that viruses are living things. Is that correct?


A: No. Living beings always have their own metabolism. Viruses, however, use the metabolism of "hosts" to reproduce.
Viruses are ultimately nothing more than "gone wild", extracellular genes or RNA molecules that infiltrate cells with the help of a sophisticated attack apparatus.
They can also be obtained in crystallized form.


1375
Q: I tried - on the Internet and in the literature - to find a suitable voltage series in which the redox couple: Bi -> Bi (3+) + 3e- can be found. Unfortunately, I couldn't get an answer from my chemistry teacher either.
Are you familiar with an "extended" series of voltages, e.g. with the voltages of (all) semimetals?
At least I would be happy if you could tell me the potential of the redox reaction mentioned above.


A: In an acidic environment is the standard potential for the following process

Bi + H2O <———> BiO+ + 2 H.+ + 3 e-

E.0 = + 0.320V

The standard potentials for less common cases can only be found in special tables. In most cases, however, the Holleman-Wiberg (textbook on inorganic chemistry; de Gruyter) can also help.

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