✔ 最佳答案
Molar mass of K = 39 g mol-1
Molar mass of K2O = 39x2 + 16 = 94 g mol-1
Molar mass of K2O2 = 39x2 + 16x2 = 110 g mol-1
Molar mass of KO2 = 39 + 16x2 = 71 g mol-1
No. of moles of K used = 3.223/39 = 0.082641 mol
If only K2O is formed:
4K + O2 → 2K2O ...... (1)
No. of moles of K2O formed = 0.082641 x (2/4) = 0.041321 mol
Mass of K2O formed = 0.041321 x 94 = 3.884 g
If only K2O2 is formed:
2K + O2 → K2O2 ...... (2)
No. of moles of K2O2 formed = 0.082641 x (1/2) = 0.041321 mol
Mass of K2O2 formed = 0.041321 x 110 = 4.545 g
If only KO2 is formed:
K + O2 → KO2 ...... (3)
No. of moles of KO2 formed = 0.082641 mol
Mass of KO2 formed = 0.082641 x 71 = 5.868 g
K2O2 must be formed.
It is impossible to form the mixture of K2O and K2O2, because the mass of the products must be smaller than 5.418 g.
Therefore, the product is the mixture of K2O2 and KO2.
Let the mass of K2O2 produced be y g.
Then, the mass of KO2 produced = (5.418 - y) g
Refer to equation (2):
No. of moles K2O2 formed = y/110 mol
No. of moles of K used to produce K2O2 = 2(y/110) = y/55 mol
Refer to equation (3):
No. of moles of KO2 formed = (5.418 - y)/71 mol
No. of moles of K used to produce KO2 = (5.418 - y)/71 mol
No. of moles of K used:
y/55 + (5.418 - y)/71 = 0.082641
0.018182y + 0.07631 - 0.014085y = 0.082641
0.004097y = 0.006331
y = 1.545
In the product mixture:
Mass of K2O2 = 1.545 g
Mass of KO2 = 5.418 - 1.545 = 3.873 g
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