兩題化學問題(英文)－jpjzhf9的部落格

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兩題化學問題(英文)

發問:

1. Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na2Co3*xH2O. When a 2.558 g sample of washing soda is heated at 125 degrees C, all the water of... 顯示更多 1. Washing soda, a compound used to prepare hard water for washing laundry, is a hydrate, which means that a certain number of water molecules are included in the solid structure. Its formula can be written as Na2Co3*xH2O. When a 2.558 g sample of washing soda is heated at 125 degrees C, all the water of hydration is lost, leaving 0.948 g of Na2CO3. What is the value of x? 答案：x=10 2. How many moles of chloride ions are in 0.0750 g of aluminum chloride? 答案：1.69*10^-3 mol Cl 可以盡量解釋清楚點怎麼得到答案的嗎？我這個人理解力比較差 @_@ 謝謝～～～更新: Cl的mole數為AlCl3的3倍是怎麼計算出來的呀 @@

最佳解答:

Ans1. Na2CO3的分子量為106 一開始含水的Na2CO3˙xH2O重量為2.558克加熱後剩下0.948克 >>>為不含水的Na2CO3重量而加熱損失2.558-0.948=1.61克 >>>加熱所脫去的H2O重量假設Na2CO3的mole數為1,H2O的mole數為 x 則(0.948/106):(1.61/18)=1:x 計算可得x=10 Ans2. aluminum chloride=AlCl3,分子量為133.34 0.075克的AlCl3=(0.075/133.34)=5.625*10^- 4 mole 而其中Cl的mole數為AlCl3的3倍所以Cl的mole數為(5.625*10^- 4)*3=1.69*10^-3 mole

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