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I'm not an expert teacher or lecturer of chemistry. I was only a student from SMA NEGERI 15 SURABAYA who had been one of the Bronze Medalist Participants of Olimpiade Sains Nasional X (2011) of Chemistry In Manado, North Sulawesi, 11 - 16 September 2011 and graduated in 2012. Now, I'm studying at Universitas Airlangga in Surabaya, Indonesia. I do love chemistry and I would like to help them who had difficulties in studying chemistry. That's why, please understand me if you found some misconcepts in my entries. Suggestions are always necessary in order to develop this blog. And I'm sorry because my English isn't so well.

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The Documents

Friday, June 17, 2011

Qualitative Analysis

Sometimes we need to identify what substance we have from its property. That reason makes us have to know the properties of chemical substances around us. Here are some examples of qualitative analysis data from Cambridge International Examination Chemistry A Level. Have a look.

(ppt. = precipitate)


From the table, we can conclude that there are differences when we react the cations with strong or weak base. For example is: Aluminium.

Al3+(aq) + 3OH-(aq) <--> Al(OH)3(s)

In excess of NaOH, aluminium will form [Al(OH)4]- that reduces the concentration of hydroxide and make the equilibrium shifts to left so that the precipitate soluble in excess.

Meanwhile, in excess of NH3, aluminium won’t form the complex compound. The excess will shift the equilibrium to right so that there are more precipitate formed.

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