Calculate the concentration of the chromate ion that should be present at the final point of the titration of 50, 00mL of a solution of KBr 0, 02mol/L with a solution of AgNO3 0, 01mol/L, if the maximum theoretical error for titration is 1.0%.
What are you using for Ksp AgBr?
What are you using for Ksp Ag2CrO4?
What are your possible answers?
To calculate the concentration of the chromate ion at the final point of the titration, we need to understand the stoichiometry of the reaction between the chromate ion and the silver ion (present in the AgNO3 solution). First, let's write the balanced chemical equation for the reaction:
2 Ag⁺(aq) + CrO₄²⁻(aq) → Ag₂CrO₄(s)
From the equation, we can see that it takes two silver ions to react with one chromate ion to form one mole of silver chromate. This means that the mole ratio between Ag⁺ and CrO₄²⁻ is 2:1.
Now let's calculate the number of moles of KBr and AgNO3 used in the titration.
For KBr:
Volume = 50.00 mL = 0.05000 L
Molarity (M) = 0.02 mol/L
Number of moles of KBr = Molarity × Volume
= 0.02 mol/L × 0.05000 L
= 0.001 mol
For AgNO3:
Volume = Same as the volume of KBr solution = 0.05000 L
Molarity (M) = 0.01 mol/L
Number of moles of AgNO3 = Molarity × Volume
= 0.01 mol/L × 0.05000 L
= 0.0005 mol
Since the mole ratio between Ag⁺ and CrO₄²⁻ is 2:1, the number of moles of chromate ions (CrO₄²⁻) present at the final point of the titration is half of the number of moles of AgNO3 used. So,
Number of moles of CrO₄²⁻ = 0.0005 mol / 2
= 0.00025 mol
Finally, to calculate the concentration of the chromate ion (CrO₄²⁻), divide the number of moles of CrO₄²⁻ by the volume of the solution used in the titration.
Volume = Same as the volume of KBr solution = 0.05000 L
Concentration = Number of moles / Volume
= 0.00025 mol / 0.05000 L
= 0.005 mol/L
Therefore, the concentration of the chromate ion (CrO₄²⁻) at the final point of the titration is 0.005 mol/L.
Note: The maximum theoretical error for titration is given as 1.0%. However, this error is related to the accuracy of the titration procedure itself and does not affect the calculation of the concentration of the chromate ion.