Calcium redox reactions

C21-0055. Describe the reactions that convert calcium phosphate to phosphoric acid. Identify Brcj)nsted acid-base reactions and redox reactions, if any. 

A jug containing calcium hypochlorite (probably as moist solid) was used as a disposal receptacle for cyanide wastes from student preparations of benzoin. When a little acetic acid residue was inadvertently added, an explosion occurred, attributed to a cyanide-chlorine redox reaction. 

In the production of formic acid, a slimy of calcium formate in 50% aqueous formic acid containing urea is acidified with strong nitric acid to convert the calcium salt to free acid, and interaction of formic acid (reducant) with nitric acid (oxidant) is inhibited by the urea. When only 10% of the required amount of urea had been added (unwittingly, because of a blocked hopper), addition of the nitric acid caused a thermal runaway (redox) reaction to occur which burst the (vented) vessel. A small-scale repeat indicated that a pressure of 150-200 bar may have been attained. A mathematical model was developed which closely matched experimental data. 

The nicotinamide nucleotide coenzymes function as electron carriers in a wide variety of redox reactions. In addition, NAD is the precursor of adenine dinucleotide phosphate (ADP)-ribose for ADP-ribosylation and poly(ADP-ribosylation) of proteins and cADP-ribose and nicotinic acid adenine dinucleotide phosphate (NAADP). They act as second messengers and stimulate increases in intracellular calcium concentrations. 

Diluted hydrochloric acid can be used to remove limestone (calcium carbonate) surrounding phosphate and silicate fossils. The reaction produces carbon dioxide, water, and aqueous calcium chloride. Write the balanced chemical equation. Is it a redox reaction Explain. 

These direct titrations form the basis of more complicated analytical procedures. Many analytical procedures are indirect and involve additional preliminary reactions of the sample before the titration can be carried out. For example, a soluble calcium salt will not take part in a redox reaction with potassium permanganate. But adding ammonium oxalate to the solution containing Ca causes the quantitative precipitation of calcium oxalate ... 

When a test tube containing copper(II) oxide and powdered charcoal (carbon) is heated, a gas and copper metal are produced in a redox reaction. If the gas is bubbled into a test tube containing limewater (aqueous calcium hydroxide solution), a milky white precipitate forms. Write a lab report of this experiment as if you had performed it in the lab. Answer the following questions in your report. 

The following equation represents the neutralization reaction between hydrochloric acid and calcium hydroxide. Determine the oxidation number for each element. Is this a redox reaction Explain. 

The spontaneity of this reaction is reflected in the AG value of — 125kJ/mol(C). The result is that the total equivalents of reduced matter produced by carbon burial are redistributed and now include some pyrite. Sulfate is removed from the water permeating the sediments and magnesium and calcium carbonates are formed. Thus, the carbon, oxygen, and sulfur cycles are coupled by a redox reaction which also includes iron. The extent of the coupling depends on the supplies of reactive organic carbon, sulfate, and reactive iron. When the reduced material is returned to contact with the atmosphere, it is oxidized and an amount of oxygen equivalent to that formed when the carbon was first buried is removed. 

Some dihydroazines are found in living organisms, and various synthesized analogues can serve as useful models for studying redox reactions involving NADH and flavines. Dihydroazine derivatives also serve as calcium channel antagonists and thus have a considerable future in the area of pharmaceutical... 

When the calcium carbonate, CaC03, in limestone is heated to a high temperature, it decomposes into calcium oxide (called lime or quick lime) and carbon dioxide. Lime was used by tbe early Romans, Greeks, and Egyptians to make cement and is used today to make over 150 different chemicals. In another reaction, calcium oxide and water form calcium hydroxide, Ca(OH)2 (called slaked lime), used to remove the sulfur dioxide from smoke stacks above power plants burning bigb-sulflir coal. The equations for all these reactions are below. Determine the oxidation number for each atom in the equation and identify whether the reactions are redox reaction or not. For each redox reaction, identify what is oxidized and what is reduced. 

Write a balanced equation for the redox reaction of calcium metal and bromine liquid to form solid calcium bromide. 

Many important redox reactions take place in water, but not all redox reactions occur in aqneons solntion. Consider the formation of calcium oxide (CaO) from calcium and oxygen ... 

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