chem-reacting masses

[匿名]

2012-04-10 5:20 am

An oxide of lead was heated in hydrogen until only lead remained. 68.5g of the oxide gave 62.1g of lead.

a)Calculate the empirical formula of the oxide

b)The oxide is known to be a mixed oxide composed of PbO and PbO2.Based on you answer in (a),deduce the mole ratio of PbO to PbO2 inthe oxide.

請解釋清楚如何做(b).
步驟要清晰點.

回答 (1)

andrew

2012-04-10 6:00 am

✔ 最佳答案

a)
Mole ratio Pb : O
= 62.1/207 : (68.5-62.1)/16
= 0.3 : 0.4
= 3 : 4

Hence, the empirical formula of the oxide = Pb3O4

b)
Let x mol be the no. of moles of PbO in the oxide of lead, and y mol be the no.of moles of PbO2.

x mol of PbO contains x mol of Pb and x mol of O.
y mol of PbO2 contains y mol of Pb and 2y mol of O.

In the oxide of lead, mole ratio Pb : O
(x + y) : (x + 2y) = 3 : 4
3(x + 2y) = 4(x + y)
3x + 6x = 4x + 4y
x = 2y
x/y = 2/1
x : y = 2 : 1

Hence, in the oxide, mole ratio PbO : PbO2 = 1 : 2

參考: andrew

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