Answer:
The molarity of the KMnO4 solution is 0.05M (option 1)
Explanation:
10 HI + 2 KMnO4 + 3 H2SO4 → 5 I2 + 2 MnSO4 + 8 H2O
This is the base.
10 moles of HI need 2 moles of KMnO4, to make 5 moles of I2 (gas)
Our solution of HI is 0,20 M which means 0,2 moles in 1 L of solution but we used 5 mL, so how many moles did we use?
Molarity . volume = Moles
0.2 moles/L . 0.005L = 0.001 moles
Notice, we had to convert 5 mL into 0.005 L
So, let's go back to begining: 10 moles of HI need 2 moles of KMnO4.
How many moles of salt, do we need for 0.001 moles of HI.
The rule of three is:
10 moles of HI ___ need ___ 2 moles of KMnO4
0.001 moles of HI __ need ___ (0.001 . 2 ) / 10 = 0.0002 moles
This is our quantity of moles, that we need from KMnO4 but this moles are in 4 mL.
Molarity = moles / L but we can also take account molarity as mM / mL (Molarity/1000)
0.0002 moles . 1000 = 0.2 mM
0.2 mM / 4mL = 0.05 M
