![]() In biological systems, phosphorus can be found as free phosphate anions in solution ( inorganic phosphate) or bound to organic molecules as various organophosphates. ![]() The various metaphosphate ions (which are usually long linear polymers) have an empirical formula of (PO Phosphate can form many polymeric ions such as pyrophosphate, (P This means that salts of the mono- and di-phosphate ions can be selectively crystallised from aqueous solution by setting the pH value to either 4.7 or 9.8.īehave as separate weak acids because the successive p K a differ by more than 4. At pH 13 or higher, the acid is completely dissociated as the phosphate ion, (PO Around pH 9.8 (mid-way between the second and third p K a values) the monohydrogen phosphate ion, [HPO , is practically the only species present. Around pH 4.7 (mid-way between the first two p K a values) the dihydrogen phosphate ion, [H At pH 1 or lower, the phosphoric acid is practically undissociated. The p K a values are the pH values where the concentration of each species is equal to that of its conjugate bases. In water solution, orthophosphoric acid and its three derived anions coexist according to the dissociation and recombination equilibria below Equilibrium As a rule, the hydrogen and dihydrogen phosphates are slightly more soluble than the corresponding phosphates.Įquilibria in solution Phosphoric acid speciation Most other phosphates are only slightly soluble or are insoluble in water. The sodium, potassium, rubidium, caesium, and ammonium phosphates are all water-soluble. Many phosphates are soluble in water at standard temperature and pressure. , which in turn is the conjugate base of orthophosphoric acid, H , which in turn is the conjugate base of the dihydrogen phosphate ion H It is the conjugate base of the hydrogen phosphate ion H(PO The phosphate ion has a molar mass of 94.97 g/mol, and consists of a central phosphorus atom surrounded by four oxygen atoms in a tetrahedral arrangement. Orthophosphates can condense to form pyrophosphates. The addition and removal of phosphate groups ( phosphorylation and dephosphorylation) are key steps in cell metabolism. Orthophosphates are especially important among the various phosphates because of their key roles in biochemistry, biogeochemistry, and ecology, and their economic importance for agriculture and industry. Phosphates may contain sulfur in place of one or more oxygen atoms ( thiophosphates and organothiophosphates). The term also refers to the trivalent functional group OP(O-)ģ in such esters. These relative weights computed from the chemical equation are sometimes called equation weights.In organic chemistry, phosphate or orthophosphate is an organophosphate, an ester of orthophosphoric acid of the form POĤRR′R″ where one or more hydrogen atoms are replaced by organic groups. For bulk stoichiometric calculations, we are usually determining molar mass, which may also be called standard atomic weight or average atomic mass.įormula weights are especially useful in determining the relative weights of reagents and products in a chemical reaction. This is not the same as molecular mass, which is the mass of a single molecule of well-defined isotopes. This is how to calculate molar mass (average molecular weight), which is based on isotropically weighted averages. The atomic weights used on this site come from NIST, the National Institute of Standards and Technology. The formula weight is simply the weight in atomic mass units of all the atoms in a given formula. When calculating molecular weight of a chemical compound, it tells us how many grams are in one mole of that substance. ![]() Using the chemical formula of the compound and the periodic table of elements, we can add up the atomic weights and calculate molecular weight of the substance.įinding molar mass starts with units of grams per mole (g/mol). The percentage by weight of any atom or group of atoms in a compound can be computed by dividing the total weight of the atom (or group of atoms) in the formula by the formula weight and multiplying by 100. If the formula used in calculating molar mass is the molecular formula, the formula weight computed is the molecular weight. This site explains how to find molar mass. The reason is that the molar mass of the substance affects the conversion. To complete this calculation, you have to know what substance you are trying to convert. In chemistry, the formula weight is a quantity computed by multiplying the atomic weight (in atomic mass units) of each element in a chemical formula by the number of atoms of that element present in the formula, then adding all of these products together.Ī common request on this site is to convert grams to moles. ![]()
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