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I am actually facing alot of problem wid calculations in chemistry, can someone pls suggest on how to improve my concept .
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chemistry paper 3 (practicals)
- Thread starter ismailmz
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I suggest u to go through moles chapter u have done in Igcse BYHEAR ALL THE FORMULAS nd i think u will be fine 
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Notes On Moles
-Define mole:1 mole of any substance is its Ar or Mr expressed in grams
-Avogadro Constant are the no. of particles (atoms or molecule) permole of any substance.The value of constant is 6 X
10^23 and is represented as L.
----no. of molecules=no. of moles X L
----no. of atoms=no. of moles of atom X L
-----------where L is 6 X 10^23
-no. of moles = mass of substance/mass of one mole
-no. of moles of gas = volume in dm3 /24 (1dm3=1000cm3)
-no. of moles of solute= conc. X volume (be careful in units either all dm3 or cm3)
-(u shud know how to rearrange an eqn.)
-when the reaction involve only gases then we can use the ratio of volumes instead of mole ratio.
-Percentage yield = actual yield/theoritical yield X100
-Percentage purity = mass of pure substance / mass of impure substance X 100
-steps for finding molecular formula
---find no. of moles(method of finding this differs according to question)
---hence find the mole ratio
---and then calculate emperical formula
---find n which is=>relative molecular mass/emperical formula mass
---then find molecular formula=>(emperical formula)n and simplify
hope it helps
-Define mole:1 mole of any substance is its Ar or Mr expressed in grams
-Avogadro Constant are the no. of particles (atoms or molecule) permole of any substance.The value of constant is 6 X
10^23 and is represented as L.
----no. of molecules=no. of moles X L
----no. of atoms=no. of moles of atom X L
-----------where L is 6 X 10^23
-no. of moles = mass of substance/mass of one mole
-no. of moles of gas = volume in dm3 /24 (1dm3=1000cm3)
-no. of moles of solute= conc. X volume (be careful in units either all dm3 or cm3)
-(u shud know how to rearrange an eqn.)
-when the reaction involve only gases then we can use the ratio of volumes instead of mole ratio.
-Percentage yield = actual yield/theoritical yield X100
-Percentage purity = mass of pure substance / mass of impure substance X 100
-steps for finding molecular formula
---find no. of moles(method of finding this differs according to question)
---hence find the mole ratio
---and then calculate emperical formula
---find n which is=>relative molecular mass/emperical formula mass
---then find molecular formula=>(emperical formula)n and simplify
hope it helps