How many milliliters of a 3.85 M solution of Fe2+ are needed to titrate 250.0 mL of a 0.125 M Cro4 2- solution?
H + CrO4 2- + Fe2+ yields to Fe3+ + Cr2O3 + H2) (not balanced)
Balance the equation.
Calculate moles CrO4^2- used. That is moles = M x L = ?
Convert moles CrO4^2- to moles Fe^2+ using the coefficients in the balanced equation.
Then M Fe^2+ = moles Fe^2+/L Fe^2+
Solve for L and convert to mL.
To determine the volume of the 3.85 M Fe2+ solution needed to titrate the 250.0 mL 0.125 M CrO4 2- solution, we need to use the balanced chemical equation and the stoichiometry of the reaction.
The balanced chemical equation for the reaction is:
3Fe2+ + 8H+ + CrO4 2- -> 3Fe3+ + Cr2O3 + 4H2O
From the balanced equation, we can see that we need a 1:3 ratio of Fe2+ to CrO4 2-.
Given that the initial volume of the CrO4 2- solution is 250.0 mL, the number of moles of CrO4 2- present can be calculated as follows:
Moles of CrO4 2- = Volume (L) x Concentration (M)
Moles of CrO4 2- = 0.250 L x 0.125 M
Moles of CrO4 2- = 0.03125 moles
Since the stoichiometry of the reaction is 1:3 between CrO4 2- and Fe2+, we can determine the number of moles of Fe2+ required by multiplying the moles of CrO4 2- by the stoichiometric ratio:
Moles of Fe2+ required = 0.03125 moles x (3 moles Fe2+ / 1 mole CrO4 2-)
Moles of Fe2+ required = 0.09375 moles
Now, we can calculate the required volume of the 3.85 M Fe2+ solution using the stoichiometry and concentration of the solution:
Volume of Fe2+ solution = Moles of Fe2+ required / Concentration of Fe2+ solution
Volume of Fe2+ solution = 0.09375 moles / 3.85 M
Volume of Fe2+ solution = 0.02435 L or 24.35 mL
Therefore, 24.35 mL of the 3.85 M solution of Fe2+ is needed to titrate the 250.0 mL solution of 0.125 M CrO4 2-.
To solve this titration problem, we need to determine the amount of Fe2+ solution required to react completely with the CrO4 2- solution.
First, let's write the balanced equation for the reaction:
H+ + CrO4 2- + Fe2+ → Fe3+ + Cr2O3 + H2O
The stoichiometry of the balanced equation indicates that the mole ratio between H+ and Fe2+ is 1:1. Therefore, the number of moles of Fe2+ required to react completely with the CrO4 2- can be calculated using the concentrations and volumes of the two solutions.
The amount of substance (in moles) is calculated using the formula:
Amount (moles) = Concentration (M) × Volume (L)
For the CrO4 2- solution:
Amount of CrO4 2- = Concentration of CrO4 2- × Volume of CrO4 2- solution
Amount of CrO4 2- = 0.125 M × 0.250 L (converting mL to L)
Amount of CrO4 2- = 0.03125 moles
Since the stoichiometry between CrO4 2- and Fe2+ is 1:1, this means that the same amount of Fe2+ is required to react with the CrO4 2-.
Now, let's calculate the volume of the Fe2+ solution required:
Amount of Fe2+ (moles) = Amount of CrO4 2- (moles) = 0.03125 moles
To find the volume of the Fe2+ solution needed, we can use the formula:
Volume (L) = Amount (moles) / Concentration (M)
Volume of Fe2+ solution = 0.03125 moles / 3.85 M
Volume of Fe2+ solution ≈ 0.00812 L
Since the volume is given in liters, let's convert it to milliliters:
Volume of Fe2+ solution = 0.00812 L × 1000 mL/L
Volume of Fe2+ solution ≈ 8.12 mL
Therefore, approximately 8.12 milliliters of the 3.85 M solution of Fe2+ are needed to titrate 250.0 mL of the 0.125 M CrO4 2- solution.