In all precipitation reactions, the ions of one substance are exchanged with the ions of another substance when their aqueous solutions are mixed. At least one of the products formed is insoluble in water. Two ionic compounds exchange ions. Reaction will not occur unless one of the products either precipitates, or is water. Dissociation, Ionic compounds – Metal + nonmetal (Type I & II) – Metal + polyatomic anion – Polyatomic cation + anion , Dissociation: when ionic compounds dissolve in water the anions and cations are separated from each other , We know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity. Process for Predicting the Products of a Precipitation Reaction: Determine…show more content… INTRODUCTION
Potassium cyanide has the formula KCN. It is a colourless crystalline salt, which has an appearance similar to that of sugar. It is also very soluble in water. Its use is very popular in the mining of gold, electroplating and the synthesis of organics. KCN is also used in jewellery for buffing and chemical gilding. This compound is also very poisonous. During hydrolysis small amounts of hydrogen cyanide are emitted from the moist solids, giving of a bitter almond smell. (K+) ions and (CN-) ions are formed from the separation of KCN.
. Iron (Fe) has long been a recognized physiological requirement for life, yet for many microorganisms that persist in water, soils and sediments, its role extends well beyond that of a nutritional necessity. Fe(II) can function as an electron source for iron-oxidizing microorganisms under both oxic and anoxic conditions and Fe(III) can function as a terminal electron acceptor under anoxic conditions for iron-reducing microorganisms. Microbial nitrate-dependent Fe(II) oxidation is known to contribute to iron biogeochemical cycling; however, the microorganisms responsible are virtually unknown. The biochemistry of Fe(II) oxidation has been studied in detail with aerobic acidophilic Fe(II) oxidizers however, much less is known about the mechanisms of neutrophilicFe(II) oxidation. Our studies further demonstrate the abundance of nitrate-dependent Fe(II) oxidizers in freshwater lake sediments and provide further evidence for the potential…show more content… Five experiments were performed in 500 ml stirred conical flasks. Fifty millilitres (50 ml) of the bacterial culture (from a chemostat running at 30°C and 48 h residence time) was added to 200 ml of growth medium in each flask. The flasks were then loosely covered with cotton wool to allow aeration. Finally, the flasks were placed on the rotary shaker with a rotation speed of 200 rpm and the temperature was maintained at 22°C in an air conditioned room/incubator. The ferric-iron and total iron concentrations in the flasks were measured initially. The pH in each flask was adjusted to 0.8, 1.37, 1.55, 1.88 and 2.06. using 98% sulphuric acid. Each experiment was carried out in triplicate. The ferrous iron concentration was monitored at specific time intervals, and by subtracting the obtained ferrous iron concentration from the total iron concentration, the ferric iron concentration was obtained at the specified time