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標題:
小小既二個既化學問題
發問:
現進行以下實驗,測定一樣本中氧化鉛(II)的質量百分比 階段1 稱取固體樣本的質量,把過量的稀硝酸加進樣本中 2 把從階段1取得的混合物過濾,去除不溶解的固體 3 把過量的氯化鈉溶液加入濾液,以沈澱氯化鉛(II) 4 收集氯化鉛(II)沈澱物,並以蒸餾水沖洗 5 把氯化鉛(II)弄乾,並稱取它的質量 以下是在實驗中取得的結果: 固體樣本的質量=9.80g 取得氯化鉛(II)的質量=9.37g 1)計算樣本中氯化鉛(II)的質量百分比 概念既問題 1)質量百分比同摩爾有咩關系? 同埋我比d公式搞到好混亂,究竟點用d公式 thx
最佳解答:
Two reactions: 1) PbO + 2HNO3 --> Pb(NO3)2 + H2O 2) Pb(NO3)2 + 2NaCl --> PbCl2 + 2NaNO3 PbCl2 is the INSOLUBLE product mass of PbCl2 = 9.37g no. of mole of PbCl2 = mass / molar mass = 9.37 / 278.2 = 0.033681 By equation 2's mole ratio, no.of mole of Pb(NO3)2 : PbCl2 = 1 : 1 So, no. of mole of Pb(NO3)2 formed in reaction 1 = 0.03381mol By equation1's mle ratio, no.of mole of PbO : Pb(NO3)2 = 1 : 1 So, no. of mole of PbO in reaction 1 = 0.03381mol By mole = mass / molar mass, Mass of PbO = 0.03381*(223.2) = 7.55g % by mass = 7.55/9.8 * 100% = 77.0% Relationship between % by mass and mole: 1) have no. of mole of product, by mole ratio in equation, 2) no. of mole of reactant can be found 3) no. of mole of reactant * molar mass = mass of reactant 4) mass of reactant / mass of sample * 100% = % by mass If you really need a Chinese version, tell me. Ask if you don't understand!
其他解答:
Billyionaire: 無打錯阿,我重新睇左幾次都無錯o_o..|||||係咪打錯字= =稀硝酸幾時變左HCl...搞到我成題睇唔明邊度黎既不溶解固體...|||||% by mass 其實一睇就睇到... 其實係同mass有關only 不過我地好多時都用1mole做基準 例如HCl 1mole 就有1mole既H 1mole既Cl 所以可以出現到 => %bm H = 1/1+35.5 x100% 當然 你都可以用2mole去做 (其實幾mole都ok) %bm H = 1x2/1x2+35.5x2 x100% = 上面 主要係同mass有關 如果你度到mass 就咁做都可以 不過我地好多時都就咁拎molar mass做...A9A39959EDCC7BE3
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