The diffrence between Fe2+ and Fe3+ is the Fe2+has a pale green color and turns violet when water is added to it. While Fe3+ forms blood red when it reacts with thiocyanate ions.
According to Hess’s law of constant heat summation, the heat absorbed or evolved in a given chemical equation is the same whether the process occurs in one step or several steps.
According to this law, the chemical equation can be treated as ordinary algebraic expression and can be added or subtracted to yield the required equation. That means the enthalpy change of the overall reaction is the sum of the enthalpy changes of the intermediate reactions.
The net reaction is
The intermediate balanced chemical reaction will be,
According to this question, 3.425g of lead oxide was reduced to form 3.105g of lead in an experiment. Since lead oxide contains both lead (Pb) and oxygen (O) element,
Mass of lead oxide = 3.425g
Mass of lead = 3.105g
Mass of oxygen = (3.425g - 3.105g) = 0.320g
Next, we convert each mass value to mole by dividing by respective molar mass
Pb = 3.105g ÷ 207.2 = 0.0149mol
O = 0.320g ÷ 16 = 0.02mol
Next, we divide each mole value by the smallest (0.0149)
Pb = 0.0149mol ÷ 0.0149mol = 1
O = 0.02mol ÷ 0.0149mol = 1.342
Multiply each ratio value by 3 to get:
Pb = 1 × 3 = 3
O = 1.342 × 3 = 4.026
The whole number ratio, approximately, of Pb and O is 3:4, hence, their empirical formula is Pb3O4.