✔ 最佳答案
Which is suitable to prepare PbCl2 (It should be PbCl2, but NOT Pb2Cl) by directly mixing with dilute HCl
lead
lead(II) carbonate
lead(II) hydroxide
lead(II) nitarate (Answer)
Lead(II) nitrate is soluble in water. When lead(II) nitrate solution is mixed with dilute HCl, PbCl2 precipitate is formed which is the only solid in the reaction mixture. Therefore, PbCl2 is easily separated by filtration.
Pb(NO3)2(aq) + 2HCl(aq) → PbCl2(s) + 2HNO3(aq)
Lead, lead(II) carbonate and lead(II) hydroxide are both insoluble in water. When each is added to dilute HCl, PbCl2 precipitate is formed. The precipitate coats on the solid reactant and separates the two reactants. This makes the reaction slow down and stop soon after the reaction starts. Besides, because the reaction mixture contains PbCl2 and the unreacted solid reactant, it is difficult to separate PbCl2 from the reaction mixture.
Pb(s) + 2HCl(aq) → PbCl2(s) + H2(g)
PbCO3(s) + 2HCl(aq) → PbCl2(s) + H2O(l) + CO2(g)
Pb(OH)2(s) + 2HCl(aq) → PbCl2(s) + 2H2O(aq)
When sulphuric acid is dissolved in water, sulphuric acid molecule become mobile.
點解係false?? conc H2SO4 唔係好唔mobile咩??
Pure sulphuric acid is a viscous liquid, in which the sulphuric acid molecules are mobile (although the mobility is low). Therefore, the word "become" is false.
In the experiment studing the rate of reaction, which of the following should be kept constant??
A)Temperature B) Total volume C) Beaker size D) no. of mole of the thiosulphate ions
ANS: ABC 點解 d 唔要 C 要??
The aim of the experiment is to studying the effect of concentration on the rate of reaction. The total volume of the solution is kept constant. If number of moles of the thiosuphate ions is kept constant, the concentration will thus be constant. To study the effect of concentration, the concentration must be varied but NOT constant.
2010-04-28 01:42:31 補充：
Beaker size 是 constant，因為要相同的 volume 做成相同的 depth of solution。
