1. Why the statement " Thermosetting plastics contain strong covalent bonds while thermoplastics do not " is incorrect? Please explain!
2. CE 08 M.C. No. 33
When calcium granules are added to water, colourless gas bubbles are formed. The mixture is then filtered to obtain a clear solution. Which of the following is correct if excess dil. HCl is added to the clear solution?
A. Gas bubbles are formed.
B. There is no visible change.
C. A white ppt is formed.
D. The clear solution turns brick red.
[Why the ans is not A? Is this a reaction between HCl and calcium hydroxide? It is a neutraliation reaction!]
Please explain!
Thz~
Chemistry past paper 2
2008-12-29 7:55 am
回答 (2)
2008-12-29 5:00 pm
✔ 最佳答案
1)Both thermosetting plastics and thermoplastics contain strong covalent bonds in their molecules but thermosetting plastics contain strong covalent bonds between molecules(cross-link) but thermoplastic does not.2) The answer is B. This a neutraliation reaction between HCl and calcium hydroxide solution. As no gas will formed during the reaction and the CaCl2 produced is soluble in water, there will be no visible change.
Equation
Ca(OH)2(aq) + 2HCl(aq) ------->CaCl2(aq) + 2H2O(l)
2008-12-29 8:19 am
1. Both of them have strong covalent bond but thermosetting plastics
has cross link while thermoplastics does not between molecules
2. You are right. It is a neutraliation reaction.H2O and CaCl2 are formed but CaCl2 is solid and doesn't soluble in water so ppt is formed
2008-12-29 17:56:05 補充：
CaCl2 is soluble in water
has cross link while thermoplastics does not between molecules
2. You are right. It is a neutraliation reaction.H2O and CaCl2 are formed but CaCl2 is solid and doesn't soluble in water so ppt is formed
2008-12-29 17:56:05 補充：
CaCl2 is soluble in water
參考: me
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