1a) How many moles of water are in 0.49742 grains? (1 grain = 0.0648 grams.)
b) If one mole of tin is formed for every mole of water decomposed, then the 3.2 grains of tin represents the same number of moles as you found in the previous question. If so, what is the mass of one mole of tin?
2) Now let us analyze the problem using our knowledge of electrons and valences.
a) Consider the decomposition of water:
2 H2O -- > 2 H2 + O2Which element is oxidized in the course of the reaction? Which is reduced? How many electrons must be transferred in the course of decomposing two molecules of water?
b) Consider the decomposition of tin(II) chloride:
SnCl2 -- > Sn + Cl2Which element is oxidized in the course of the reaction? Which is reduced? How many electrons must be transferred in the course of decomposing one molecule of SnCl2?
c) How many moles of Sn are electrochemically "equivalent" to one mole of water? (Hint: Write the chemical equations above so that they refer to the same number of electrons transferred and then compare the stoichiometric numbers for water and tin.)
3) The Faraday constant, 96485 coulombs per mole, was named after Michael Faraday; it is the magnitude of the electrical charge of one mole of electrons. What quantity of electrical charge passed through Faraday's electrochemical apparatus to decompose 0.49742 grains of water?
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