Qualification > Sciences
CHEMISTRY. P3. CIE.. advice and titrations?
joggingday:
--- Quote from: ruby92 on May 19, 2010, 04:19:50 pm ---M/j 2009 variant 32
c step 3 4 5???
--- End quote ---
Step 3:
To calculate moles of ethanedioate ions that reacted with the KMnO4 : Use the mol ratio from 2nd step. You find that for every 2 mol of MnO4- ions, there are 5 moles of ethanedioate ions. So :
Answer = (Mol of KMnO4/2) * 5
Step 4: You know the volume of FB3 used in the titration was 25 cm3. So molarity = mol of ethanedioate ions/volume in dm3
Volume in dm3 will be 25/1000= 0.025
Step 5: You now have the concentration in mol dm-3 from step 4. This tells you that there are x mol in 1000cm3. You have to multiply this value by 1000 to get the "total" moles. Then divide this answer by the volume of FB2 used (which should be between 42.5 and 43.0 cm3)
Step 6: From step 5 you have the number of moles per dm3. To find the amount of grams per dm3, simply multiply your answer in step 5 by the Mr, to get the mass per dm3. In this case it will be:
concentration * 126
Hope this helps
Ro1024:
hey, could anyone who does the exam earlier post some of the questions that come up?
cos i am reallly crap at practicals! let me know, i do it on thursday! PAPER 31...
Anyone??
ruby92:
--- Quote from: joggingday on May 19, 2010, 06:15:45 pm ---
Step 3:
To calculate moles of ethanedioate ions that reacted with the KMnO4 : Use the mol ratio from 2nd step. You find that for every 2 mol of MnO4- ions, there are 5 moles of ethanedioate ions. So :
Answer = (Mol of KMnO4/2) * 5
Step 4: You know the volume of FB3 used in the titration was 25 cm3. So molarity = mol of ethanedioate ions/volume in dm3
Volume in dm3 will be 25/1000= 0.025
Step 5: You now have the concentration in mol dm-3 from step 4. This tells you that there are x mol in 1000cm3. You have to multiply this value by 1000 to get the "total" moles. Then divide this answer by the volume of FB2 used (which should be between 42.5 and 43.0 cm3)
Step 6: From step 5 you have the number of moles per dm3. To find the amount of grams per dm3, simply multiply your answer in step 5 by the Mr, to get the mass per dm3. In this case it will be:
concentration * 126
Hope this helps
--- End quote ---
thanks a lot :)
just one question in step 5 we multiply the conc found in step 4 with 1000?
Ro1024:
are there titrations in paper 31?????
AS-Girl:
--- Quote from: Ro1024 on May 19, 2010, 08:53:58 pm ---are there titrations in paper 31?????
--- End quote ---
God only knows..
Reminder: No discussion of exams or predictions!!
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version