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Saturday, October 6, 2007

Chemistry Question - Metals / Periodic Table

Halo Students,

Chem Practical is round the corner and Chem Paper 2 in less than 3 week time.
Hope your preparation is going well.

Since this is the weekend, i think you might want somemore conceptual chem questions to think it through. Here is the start of more to share:

Q)Calcium Carbonate decomposes more readiliy on heating than sodium carbonate. Suggest a reason for this.

CaCO3 --> CaO + CO2
Na2CO3 --> Na2O + CO2

Think about it.

Rgds
Sean
SimpleChemConcepts
"Learning Experience with A Difference"

5 comments:

zhengning said...

I would like to give this a try, not sure of the correct answer however.

Hmmm is it because Na is a more reactive metal as compared to Ca? The more stable the compound, the higher the temperature is needed for decomposition. Hence, Na2CO3 will takes a longer time...

I think? hahaha.

lijun(: said...

actually, i do somewhat understand this, but i can never get it penned down in words. =/

all i know is that,
since sodium is more reactive than calcium, it will form a more stable carbonate than calcium. hence, sodium carbonate will not decompose as easily as calcium carbonate.

can u please explain this in greater detail? thanks.

Anonymous said...

Sodium is higher than calcium in the reactivity series, thus making it more reactive and forming more stable compounds. Thus calcium carbonate decomposes more readily than sodium carbonate.

I hope I'm right. :\

Sean Chua said...

Halo Zhengning, Lijun and Anonymous.

Well Done. In fact all three of you got the concepts spot-on and i thought your answers are GOOD.

"Na is more reactive than Ca, and thus forms a much stable compound with Carbonate. It is like Na is so reactive that they "hold" carbonate so tightly and strongly that they requie higher heat energy to break the ionic bondig"-informal annswer for understanding.

Rgds,
Sean
SimpleChemConcepts
"Learning Experience with A Difference"

FluffySnow said...

hmm. IMO, shouldn't Calcium carbonate be more stable than sodium carbonate?

Calcium carbonate is infact Ca2(CO3)2, which means that the electrostatic forces between the calcium and carbonate ion should be stronger as compared to Sodium carbonate, which only has 2 sodium ions forming bonds with a single carbonate ion.

So, shouldn't calcium carbonate, with 2 calcium ions attached to 2 carbonate ions, be more stable?