回應(會考化學)

Sampson:
首先唔該你解答左我上次既問題先但係我想問下ｅ條....

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1st statement: Carbon dioxide can effectively be prepared by the action of dilute sulphuric acid on calcium carbonate.

2nd statment: Carbonates react with dilute acids to give carbon dioxide.

你解釋好似有d問題咁..答案係c ...但係應該係 1st statement錯因為c 係話 1st statement錯 2nd 岩..仲有..1st statement..係 dil. H2SO4 + CaCO3...而唔係 metal + dil. HNO3其實...1st statement 錯既 reason係唔係..."effectively" e個字呢因為..H2SO4 + CaCO3 -> CaSO4 + H2O + CO2但係唔係...好 effectively..??其實我都唔知我岩唔岩 化學友 你點睇??

化學友:
唔該晒阿sampson，手快快將個'o岩'字寫成'錯'字tim,thanks ah。 (e 家改返啦。)

不過可能化學友寫得簡單左d令你誤會左2nd statement。其實，化學友發覺好多同學仔一到考試就會唔小心咁以為metals、oxide、hydroxide或者carbonate + conc.H2SO4會出SO2，而如果加dil. HNO3就會出NO。因為2nd statement係話dil. acid,maryeun就覺得dil.HNO3+carbonate應該出NO唔係CO2，所以佢認為2nd statement都係錯嘅。

至於1st statement，你條equation係o岩o架，而因為CaSO4 formed係solid，佢會coats on the surface of CaCO3(s)，阻止H2SO4接觸CaCO3(s)。所以reaction will stop soon，而得好少CO2收集到。就因為咁，o個方法唔effective去prepare CO2。明白嗎sampson。