neutralization (urgent)

2011-07-06 9:25 pm

Why can limewater react with aqueous potassium sulphate?
I ask this because it seems that K2SO4 is a salt rather than an acid. Is it because K2SO4 is an acidic salt, therefore it can react with an alkali? But if I'm not mistaken, it is formed between strong acid (H2SO4) and strong alkali (KOH), and it should be neutral like NaCl.
Please tell me why there is a reaction between them and point out any misconceptions in my deduction.

thanks

回答 (1)

fooks

2011-07-07 12:39 am

✔ 最佳答案

Thereis no neutralization reaction between limewater and potassium sulphatesolution. You are right that potassium sulphate is a neutral salt, as it is thesalt resulting from the neutralization of a strong acid H2SO4and a strong alkali KOH.

The reaction between limewater and potassium sulphate solution is precipitation,but NOT neutralization. Limewater is calciumhydroxide solution which contains mobile calcium ions and hydroxide ions, whilepotassium sulphate solution contains mobile potassium ions and sulphateions. When the two solutions are mixedtogether, calcium ions combine with sulphate ions to give calcium sulphateprecipitation. This is because calciumsulphate is only very slightly soluble in water. The equation is:
Ca(OH)2(aq) + K2SO4(aq) → CaSO4(s) + 2KOH(aq)
OR: Ca²⁺(aq)+ SO4²⁻(aq) → CaSO4(s)

參考: Tsui

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