化學問題 (莫耳數及原子量, 英文好的比較適合進來)...

[匿名]

2009-09-14 6:31 pm

1. 如果有一個人每一秒鐘數一個金元素(gold atom), 那麼在八十年內, 總共數了多少"克"的 gold atom?

2. The vitamin A molecule has the formula C20H30O, and a molecule of vitamin A2 has the formula C30H28O. Determine how many moles of vitamin A2 contain the same number of atoms as 1.000 mol of vitamin A.

3. Aluminum oxide (Al2O3) occurs in nature as a mineral called corundum. Its density is 3.97 g cm-3 (cm的負三次方). Calculate the number of atoms of aluminum in 15.0 cm3 of corundum.

就這三題了, 麻煩詳解一下, 謝謝! :)

我很急, 希望能盡快回答...

更新1:

Uncle Michael, 謝謝你的回答, 不過我還有一個問題, 為什麼第二題的 "No. of moles of atoms in vitamin A" 是 1x51atoms, 是有什麼公式嗎? 能不能列出來給我這化學白痴.... 謝謝! :)

回答 (1)

Uncle Michael

2009-09-14 8:47 pm

✔ 最佳答案

1.
應是每一秒鐘數一個金原子（gold atom），而不是數一個金元素。

每年平均有 365.25 天，每天有 24 小時，每小時有 3600 秒。
80 年的總秒數 = 80 x 365.25 x 24 x 3600 = 2.525 x 109 秒
金原子的數目 = 2.525 x 109 個

每莫耳的金有 6.023 x 1023 個金原子。
金的莫耳數 = (2.525 x 109)/(6.023 x 1023) = 4.192 x 10-15

金的原子量 = 197.0
總共數了金的質量 = 197 x (4.192 x 10-15) = 8.258 x 10-13 克

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2.
No. of moles of vitamin A = 1 mol
No. of atoms in each vitamin A molecule = 20 + 30 + 1 = 51 atoms
No. of moles of atoms in vitamin A = 1 x 51 = 51 mol

No. of moles of atoms in vitamin A2 = 51 mol
No. of atoms in each vitamin A2 molecule = 30 + 28 + 1 = 59 atoms
No. of moles of vitamin A2 = 51/59 = 0.8644 mol

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3.
Mass of Al2O3 = density x volume = 3.97 x 15 = 59.55 g

Molar mass of Al2O3 = 27x2 + 16x3 = 102 g/mol
No. of moles of Al2O3 = 59.55/102 = 0.5838 mol

Each mole Al2O3 contains 5 moles of atoms.
No. of atoms = 0.5838 x 5 x (6.023 x 1023) = 1.758 x 1024 atoms
(Actually, this is the number of ions, but not atoms)

2009-09-16 02:07:11 補充：
因為每個 molecule 中有 51 個 atoms，所以每 mole molecules 中有 51 moles of atoms。

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