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From Wikipedia

Copper sulfide

Copper sulfides describe a family of chemical compounds and minerals with the formula CuxSy. Both minerals and synthetic materials comprise these compounds. Some copper sulfides are economically important ores.

Prominent copper sulfide minerals include Cu2S (chalcocite) and CuS (covellite). In the mining industry, the minerals bornite or chalcopyrite, which consist of mixed copper-iron sulfides, are often referred to as "copper sulfides". In chemistry, a "binary copper sulfide" is any binary chemical compound of the elements copper and sulfur. Whatever their source, copper sulfides vary widely in composition with 0.5 ≤ Cu/S ≤ 2, including numerous non-stoichiometric compounds.

Known copper sulfides

The naturally occurring mineral binary compounds of copper and sulfur are listed below. There are probably more yet to be discovered, for example investigations of "blaubleibender covellite" (blue remaining covellite) formed by natural leaching of covellite (CuS) indicate that there are other metastable Cu-S phases still to be fully characterised.

Classes of copper sulfides

Copper sulfides can be classified into three groups:

Monosulfides, 1.6 ≤ Cu/S ≤ 2: their crystal structures consist of isolated sulfide anions that are closely related to either hcp or fcc lattices, without any direct S-S bonds. The copper ions are distributed in a complicated manner over interstitial sites with both trigonal as well as distorted tetrahedral coordination and are rather mobile. Therefore, this group of copper sulfides shows ionic conductivity at slightly elevated temperatures. In addition, the majority of its members are semiconductors.

Mixed monosulfide and disulfide compounds of copper contain both monosulfide (S2−) as well as disulfide (S2)n− anions. Their crystal structures usually consist of alternating hexagonal layers of monosulfide and disulfide anions with Cu cations in trigonal and tetrahedral interstices. CuS, for example, can be written as Cu3(S2)S. Several nonstoichiometric compounds with Cu:S ratios between 1.0 and 1.4 also contain both monosulfide as well as disulfide ions. Depending on their composition, these copper sulfides are either semiconductors or metallic conductors.

At very high pressures, a copper disulfide, CuS2, can be synthesized. Its crystal structure is analogous to that of pyrite, with all sulfur atoms occurring as S-S units. Copper disulfide is a metallic conductor due to the incomplete occupancy of the sulfur p band.

Oxidation states of copper and sulfur

The bonding in copper sulfides cannot be correctly described in terms of a simple oxidation state formalism because the Cu-S bonds are somewhat covalent rather than ionic in character, and have a high degree of delocalization resulting in complicated electronic band structures. Although many textbooks (e.g. ) give the mixed valence formula (Cu+)2(Cu2+)(S2–)(S2)2– for CuS, X-ray photoelectron spectroscopic data give strong evidence that, in terms of the simple oxidation state formalism, all the known copper sulfides should be considered as purely monovalent copper compounds, and more appropriate formulae would be (Cu+)3(S2–)(S2)– for CuS, and (Cu+)(S2)− for CuS2, respectively. Further evidence that the assignment of the so-called "valence hole" should be to the S2 units in these two formulae is the length of the S-S bonds, which are significantly shorter in CuS (0.207 nm) and CuS2 (0.203 nm) than in the "classical" disulfide Fe2+(S2)2− (0.218 nm). This bond length difference has been ascribed to the higher bond order in (S-S)− compared to (S-S)2− due to electrons being removed from a π* antibonding orbital. NMR studies on CuS show that there are two distinct species of copper atom, one with a more metallic nature than the other. and this apparent discrepancy with the X-ray photo-electron spectrum data simply highlights the problem of assigning oxidation states in a mixed-valence compound.



From Yahoo Answers

Question:I've been getting results that range from about 100 g to 350 grams and im not sure how many i need, or how to calculate it properly Thanks

Answers:If it's anhydrous it's 159.61 g, if it's the pentahydrate then it's 249.68 g. This because the molar mass is g mol-1 and molarity is moles litre-1. The molar mass made up to 1.0 litre will give you 1.0 mol solution.

Question:1. Why would you gently heat the sulphuric acid + copper oxide? 2. Why would you filter the mixture? 3. How could you get crystals of copper sulphate from the solution of copper sulphate?

Answers:1) Heat the mixture to increase the rate of reaction between copper oxide and sulphuric acid: CuO(s) + H2SO4(aq) --> CuSO4(aq) + H2O(l) 2) Filter the mixture to remove unreacted copper oxide. 3) Allow water to slowly evaporate from the solution. As the concentration of copper sulphate increases it will begin to crystallise out of solution.

Question:I know that copper oxide + sulphuric acid => copper sulphate + water but I'd like to know if this process reverses if there's an abundance of sulphuric acid relative to the amount of copper.

Answers:They may dissolve, depending on the amount of water in your acid, but no the process will Not reverse. To reverse the reaction you need a strong base. The experiment I used was using a saturated solution of copper sulfate mixed with a saturated solution of sodium hydroxide (in water). A double replacement reaction occurred, forming soluble sodium sulfate and insoluble copper oxide. Filter the oxide and wash thoroughly. You should get fairly pure copper (II) oxide.

Question:1)do they use any of these substances in anything please list products if they do. 2)Is phosphoric acid used in masonry products 3)what is the history of these substances(when first discovered and uses back then) is it true that phoshoric acid reacts violently when combined with sulphates including copper sulphate to "science teacher" do you mean masonry as on the bricks or masonry cleaner

Answers:Phosphoric acid : Phosphoric acid as a chemical reagent Pure 75-85% aqueous solutions (the most common) are clear, colourless, odourless, non-volatile, rather viscous, syrupy liquids, but still pourable. Phosphoric acid is very commonly used as an aqueous solution of 85% phosphoric acid or H3PO4. Because it is a concentrated acid, an 85% solution can be corrosive, although not toxic when diluted. Because of the high percentage of phosphoric acid in this reagent, at least some of the orthophosphoric acid is condensed into polyphosphoric acids in a temperature-dependent equilibrium, but for the sake of labeling and simplicity, the 85% represents H3PO4 as if it were all orthophosphoric acid. Other percentages are possible too, even above 100%, where the phosphoric acids and water would be in an unspecified equilibrium, but the overall elemental mole content would be considered specified. When aqueous solutions of phosphoric acid and/or phosphate are dilute, they are in or will reach an equilibrium after a while where practically all the phosphoric/phosphate units are in the ortho- form. Preparation of hydrogen halides: Phosphoric acid reacts with halides to form the corresponding hydrogen halide gas (steamy fumes are observed on warming the reaction mixture). This is a common practice for the laboratory preparation of hydrogen halides. 3NaCl(s)+H3PO4(l)->NaH2PO4(s)+HCl(g) 3NaBr(s)+H3PO4(l)->NaH2PO4(s)+HBr(g) 3NaI (s)+H3PO4(l)->NaH2PO4(s)+HI (g) Rust removal : Phosphoric acid may be used by direct application to rusted iron, steel tools or surfaces to convert iron(III) oxide (rust) to a water soluble phosphate compound. It is usually available as a greenish liquid, suitable for dipping (acid bath), but is more generally used as a component in a gel, commonly called naval jelly. As a thick gel, it may be applied to sloping, vertical, or even overhead surfaces. Care must be taken to avoid acid burns of the skin and especially the eyes, but the residue is easily diluted with water. When sufficiently diluted it can even be nutritious to plant life, containing the essential nutrients phosphorus and iron. It is sometimes sold under other names, such as "rust remover" or "rust killer". It should not be directly introduced into surface water such as creeks or into drains, however. After treatment, the reddish-brown iron oxide will be converted to a black iron phosphate compound coating that may be scrubbed off. Multiple applications of phosphoric acid may be required to remove all rust. The resultant black compound can provide further corrosion resistance (such protection is somewhat provided by the superficially similar Parkerizing and blued electrochemical conversion coating processes.) After application and removal of rust using phosphoric acid compounds, the metal should be oiled (if to be used bare, as in a tool) or appropriately painted, most durably by using a multiple coat process of primer, intermediate, and finish coats. Processed food use : It is also used to acidify foods and beverages such as various colas, but not without controversy as to its health effects. It provides a tangy taste, and being a mass-produced chemical, is available cheaply and in large quantities. The low cost and bulk availability is unlike more expensive natural seasonings that give comparable flavors, such as ginger for tangyness, or citric acid for sourness, obtainable from lemons and limes. (However most citric acid in the food industry is not extracted from citrus fruit, but fermented by Aspergillus niger mold from scrap molasses, waste starch hydrolysates and phosphoric acid.) It is labeled as E number E338. Biological effects on bone calcium : Phosphoric acid, used in many soft drinks (primarily cola), has been linked to lower bone density in epidemiological studies. For example a study[2] using dual-energy X-ray absorptiometry rather than a questionnaire about breakage, provides reasonable evidence to support the theory that drinking cola results in lower bone density. This study was published in the American Journal of Clinical Nutrition. A total of 1672 women and 1148 men were studied between 1996 and 2001. Dietary information was collected using a food frequency questionnaire that had specific questions about the number of servings of cola and other carbonated beverages and that also made a differentiation between regular, caffeine-free, and diet drinks. The paper finds statistically significant evidence to show that women who consume cola daily have lower bone density. The study also suggests that further research is needed to confirm the findings. On the other hand, a study funded by Pepsi suggests that low intake of phosphorus leads to lower bone density. The study does not examine the effect of phosphoric acid, which binds with magnesium and calcium in the digestive tract to form salts that are not absorbed, but rather, it studies general phosphorus intake. However, a well-controlled clinical study by Heaney and Rafferty using calcium-balance methods found no impact of carbonated soft drinks containing phoshporic acid on calcium excretion. The study compared the impact of water, milk and various soft drinks (two with caffeine and two without; two with phosphoric acid and two with citric acid)on the calcium balance of 20- to 40-year-old women who customarily consumed ~3 or more cups (680 ml) of a carbonated soft drink per day. They found that, relative to water, only milk and the two caffeine-containing soft drinks increased urinary calcium, and that the calcium loss associated with the caffeinated soft drink consumption was about equal to that previously found for caffeine alone. Phosphoric acid without caffeine had no impact on urine calcium, nor did it augment the urinary calcium loss related to caffeine. Because studies have shown that the effect of caffeine is compensated for by reduced calcium losses later in the day , Heaney and Rafferty concluded that the net effect of carbonated beverages including those with caffeine and phosphoric acid -- is negligible and that the skeletal effects of carbonated soft drink consumption are likely due primarily to milk displacement. Other chemicals such as caffeine (also a significant component of popular common cola drinks) were also suspected as possible contributors to low bone density, due to the known effect of caffeine on calciuria. One other study, comprised of 30 women over the course of a week suggests that phosphoric acid in colas has no such effect, and postulates that caffeine has only a temporary effect which is later reversed. The authors of this study conclude that the skeletal effects of carbonated beverage consumption are likely due primarily to milk displacement.[6] (Another possible confounding factor may be an association between high soft drink consumption and sedentary lifestyle.) Medical use Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed. Phosphoric acid is also an ingredient in over the counter anti-nausea medications which also contain high levels of sugar (glucose and fructose). It should not be used by diabetics without consultation with a doctor. Phosphoric acid is also used as a catalyst in the synthesis of aspirin because it provides a larger number of hydrogen ions with less contamination when compared to hydrochloric acid and sulfuric acid. Uses of Copper Sulphate ; In organic synthesis Copper sulfate is employed in organic synthesis.The anhydrous salt catalyses the transacetalization in organic synthesis. The hydrated salt reacts with potassium permanganate to give an oxidant for the conversion of primary alcohols. In school chemistry demonstrations Copper sulfate is a commonly included chemical in children's chemistry sets and is often used in high school crystal growing. and copper plating experiments. Due to its toxicity, it is not recommended for small children. Copper sulfate is often used to demonstrate an exothermic reaction, in which steel wool or magnesium ribbon is placed in an aqueous solutio

From Youtube

SYSF Youtube Video Competition 2008 :Obtaining anhydrous copper(II) sulphate crystals from hydrated copper(II) crystals.

Silver Nitrate Crystallization :A copper wire is placed in a test tube containing 45 ml of 0.1 M AgNO3(aq). The greater the concentration of Silver Nitrate is, the more crystalls will be formed. NOTE: This was pure silver crystal which were formed.