Because their hydration energy is larger than their lattice energy, calcium carbonate and calcium hydroxide are soluble in acetic acid. Calcium carbonate is also soluble in hydrochloric and sulfuric acids.
Calcium carbonate is the most common form of calcium on Earth. It is found in many minerals including chalk, plaster of Paris, and limestone. Calcium carbonate has a very low solubility in water (about 2 grams per liter), so it does not dissolve readily. However, it can be dissolved in strong acids such as hydrochloric or sulfuric acid. The presence of carbon dioxide gas during the extraction with acid prevents any further reaction with other substances in the sample.
Calcium carbonate is used as a food preservative because it inhibits the growth of bacteria that cause flavor and color changes in foods. When added at levels recommended by government agencies, calcium carbonate prevents sprouting in seeds and fruits, and it inhibits mold growth in bread. It is also used as a filler to increase the weight of tablets and capsules. Because it does not dissolve in water, calcium carbonate cannot be ingested orally. Instead, it must be administered via an intravenous, intramuscular, or subcutaneous route.
In pure water, calcium carbonate is very slightly soluble (47 mg/L at typical atmospheric CO2 partial pressure, as illustrated below). This is referred to as the bicarbonate ion. Calcium bicarbonate is far more soluble in water than calcium carbonate; in fact, it only occurs in solution. As with many other minerals, the presence of other ions can change the solubility of calcium carbonate. For example, if there is a large amount of alkalinity present in the water, then less of the bicarbonate ion will be available to complex with calcium and more calcium carbonate will remain in solution.
Calcium carbonate is used as a food additive and nutritional supplement. It forms a solid that is odorless and tasteless when dry and white when crushed for use as a filler or preservative in foods such as candy, cookies, breads, and cakes. When dissolved in water, calcium carbonate produces calcium and carbon dioxide gas. This action is what allows for the setting of milk into cheese and the formation of bones from calcium carbonate during skeletal development in humans and other animals.
There are two main types of calcium carbonates: calcite and aragonite. Both are insoluble under standard conditions, but aragonite is more soluble in warm water with low pH levels. The difference between these two minerals is how their crystals are arranged inside their grains.
Calcium carbonate solubility was also evaluated at pH 7.5, 6.0, and 4.5 with two CO(2) environments (0.3 and 152 mmHg) above the solution. The solubility of each calcium salt increased as the pH rose. However, each salt created a distinct pH in distilled water, influencing its solubility value. At a pH of 7.5, the solubilities of CaCO(3) and CaHPO(4)·H(2)O were 0.097 and 0.0015 g/L, respectively. At pH 6.0, the solubilities of CaCO(3) and CaHPO(4) increased to 0.25 and 0.035 g/L, respectively. At pH 4.5, the solubilities of both compounds were highest, reaching 0.5 and 0.075 g/L, respectively.
The results indicate that the solubility of calcium carbonate increases as the pH of the solution rises. However, due to different pH values for each compound, the solubility values are not equal. At a pH of 7.5, calcium carbonate is soluble in water, whereas calcium phosphate is only slightly soluble under these conditions.
At pH 6.0, both compounds are highly soluble. Calcium carbonate is more soluble than calcium phosphate under these conditions.
A calcium salt of acetic acid, calcium acetate is a chemical substance. Ca(C2H3O2)2 is the formula for it. Calcium acetate is its common name, whereas calcium ethanoate is its scientific name. It is a white or off-white crystalline compound that is soluble in water.
Calcium acetate is used as a food preservative and as a fertilizer component. It prevents fruit flies and other insects from eating stored products that contain sugar. When applied as a fertilizer, it increases the yield of crops such as corn and soybeans.
Calcium acetate is used as a precursor to make other chemicals. For example, it can be converted into calcium aceteic acid by heating it with soda ash (sodium carbonate). This acid is used as a surface-active agent in paints and cleaners.
Calcium acetate is used as a component in some anticaking agents for use in baked goods. It acts as a desiccant so the product does not become soggy during storage.
Calcium acetate is used as a buffering agent in medicines and laboratory reagents. It controls the pH of solutions without affecting their temperature. This property makes it useful in medications and laboratory experiments where the solution cannot be cooled to prevent any pain or damage being caused by the introduction of a cold virus or bacteria.
Calcium acetate is therefore a strong electrolyte, whereas calcium sulfate is a weak electrolyte. Unfortunately, the solubility criteria are useless when it comes to acids. Water dissolves a wide range of weak acids. Sulfuric acid, a powerful electrolyte, appears in the list. Hydrochloric acid, another strong electrolyte, also appears in the list. Thus, the list is not useful for determining the strength of electrolytes.
Acids can be divided into two groups: strong and weak. Weak acids don't carry a charge across a membrane, while strong acids do. Carboxylic acids are weak acids. They don't carry a charge because they have been oxidized (have their electrons removed). Strong acids include sulfuric acid, phosphoric acid, and hydrochloric acid. These acids can cross membranes because they are charged molecules. When hydrochloric acid crosses a membrane it clings to the surface of the membrane like glue. This is why hydrochloric acid is so effective at digesting proteins.
Calcium salts are only weak acids. They won't carry an electric charge across a membrane. Calcium ions will, however. Therefore, calcium salts are not as effective at crossing membranes as stronger acids. Calcium acetate is more soluble than calcium sulfate because they are both acids but calcium acetate is a strong acid so it can cross membranes more easily.
Carbonate, being a strong base, will undergo consecutive transformations into HCO3 (aq) and H2CO3 (aq), releasing gaseous CO2. Because the sulfate ion is a weak basic, it does not protonate considerably, thus calcium sulfate's solubility improves very little in acidic solution. Sulfate also has a high molar mass, so its presence in large quantities can be expected to have an impact on the viscosity of the solution.
Calcium carbonate, on the other hand, is readily soluble in acid. Its solubility increases as the pH decreases, because the hydroxide ion is able to replace some of the hydrogen ions that would otherwise remain complexed by the carbonate molecule.
At low pH values, calcium carbonate dissolves completely, leaving only calcium and oxygen atoms behind. The resulting precipitate is called calcite.
At higher pH values, the calcium carbonate molecules begin to deprotonate instead, yielding calcium ions and CO32- ions. This process continues until all the available carbonic acid has been consumed, leaving only pure water behind. The resulting solid is called aragonite.
Calcium sulfate hemihydrate, or just "calcite," is the most abundant form of calcium carbonate in nature. It can be found in sedimentary rocks, especially limestone, and is the main component of bones and teeth.