Electrochemical Equivalent Weight
Calculate the electrochemical equivalent weight, EW = M ÷ n, dividing the element's molar mass M (g/mol) by the number of electrons exchanged n (valence). The result, in g/eq, is the mass associated with transferring one mole of electrons and appears in nearly every electrochemical calculation: Faraday's law, electrochemical corrosion rate, electrodeposition and anode sizing. For divalent iron (Fe²⁺), for example, EW = 55.85 ÷ 2 ≈ 27.9 g/eq. Enter the molar mass and the number of electrons exchanged.
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Peso equivalente eletroquímico
O peso equivalente (ou massa equivalente) de um elemento numa reação eletroquímica é a massa que corresponde à transferência de um mol de elétrons. Ele se obtém dividindo a massa molar pelo número de elétrons trocados na reação: EW = M ÷ n. Para o ferro que se oxida a Fe²⁺ (n = 2), EW = 55,85 ÷ 2 ≈ 27,9 g/eq; para o alumínio a Al³⁺ (n = 3), EW = 26,98 ÷ 3 ≈ 9,0 g/eq. O conceito é a ponte entre carga elétrica e massa em toda a eletroquímica. Pela lei de Faraday, a passagem de 96.485 coulombs (1 faraday, a carga de um mol de elétrons) deposita ou consome exatamente um peso equivalente da substância. Por isso o EW aparece em todo cálculo de eletrodeposição (quanto metal se deposita por uma dada corrente), de taxa de corrosão eletroquímica (relacionando corrente de corrosão a perda de massa) e de dimensionamento de ânodos. Saber identificar corretamente o n (o estado de oxidação envolvido) é o ponto que mais gera erros. Informe a massa molar e o número de elétrons trocados.
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