sheanhung

I have already understand the function of phenol. It provides an intermidiate state before Bromine molecules able to bleach the methyl red. Or in other words, it is use to observe the time taken for Bromine molecules to react completely with phenol and free bromine molecules appear in the solution. Since all the volume and concentration of reactants remain the same, the experiment can be done on different temperature to compare the rate of reaction.

I have learned 2 different opinions on 'work done ON/BY the system'. 1. When there is compression to the system, then it is work done ON the system and the value is positive. Whereas, when the system undergoes expansion, then it is work done BY the system and the value is negative. 2. When the system undergoes compression, the work done ON the system is positve value. While for the same situation, the work done BY the system is negative value. When the system undergoes expansion, the work done ON the system is negative value. But, the work done BY the system is positive value when the system undergoes expansion. I am so confusing on it!!!!

woelon, thx for ur help. well, what i understand about the role of phenol in this experiment is it react with bromine to form tribromophemol(C6H2Br3OH) and HBr. when all the phenol has reacted, bromine contimuously produced in the first reaction bleaces the methyl red. The aim of this experiment is to determine the activation energy of the reaction between bromide and bromate ions in acid solution. I dont understand why phenol is needed. How much of the reaction between bromide and bromate ions is completed after time t? (what is the meaning and how to calculate??)

The first test tube with 10cm3 of 0.01M phenol, 10cm3 of bromide/bromate solution(0.0833M KBr & 0.0167M KBrO3) and 4 drops of Methyl Red are prepared. The second test tube fill with 5cm3 of 0.3M H2SO4. The two test tube immersed in water bath (75*C) and mix the two content of the test tubes. Repeat the experiment for 65*C, 55*C.........15*C. Some questions: 1. What is the function of phenol? 2. How much of the reaction between bromide and bromate ions is completed after time t? (what is the meaning and how to calculate??) 3. If the activation energy is doubled, would the rate of reaction be expected to increase or decease or remain unaffected? Thx ~

thank you so much to u all! Finally i finished my report just in time!

lol....u r asking the same question as i did ~ R u utar student??

Question: In copper sulfate, there are clearly two modes of binding of hydrated water. What are they? What is the structure of CuSo4.5H2O? Who first determined this structure and how? It is a difficult question for me.

Thx, but i need to draw the structure out, headach v_v. Does anyone has the drawing structure?

Anyone has the structure of it? or link? And what is the pH value of this molecule?

thx~

I have done the experiment by adding boric acid, methanol and con. sulphuric acid in a test tube. Vapour produced gives a green flame when tested with burning ignited stick. Anyone know the equation for that?? from what i have discovered was H3BO3 + 3CH3OH -----> B(OCH3)3 + 3H20 but i am not sure the function of con. sulphuric acid, so i dont know where to put it in the equation

From what i know is boric acid -------->methanoic acid------>borin oxide. But what is the condition and reagents are needed? Pls help me, if can in details~