An EDTA solution is standardised against high-purity CaCO3 by dissolving 0.4835 g CaCO3 in HCl, adjusting the pH to 10 with ammoniacal buffer and titrated with an EDTA solution. If 35.18ml were required for the titration, what was the molarity of the EDTA solution?
Step 1.
Moles CaCO3 = 0.4835/100.0869 g/mol
= 0.0049 mol.
Step 2. ??
If anyone could help that would be great, Thank you.
First, note that you can't throw all of those numbers after 0.0049 away. You have 4 places in 0.4835 and you should have AT LEAST 4 in the answer. I usually carry one more place and round at the end.
Ca^2+ + EDTA ==> Complex
mols EDTA = mols CaCO3
Then M EDTA = mols/L solution = 0.004830/0.03518 = ? M EDTA
Step 2: Finding the Molarity of the EDTA solution
To find the molarity (M) of the EDTA solution, we need to determine the number of moles of EDTA used in the titration.
From the question, we know that 35.18 mL of EDTA solution was required to titrate 0.4835 g of CaCO3.
Since the equation for the reaction between EDTA and CaCO3 is:
CaCO3 + EDTA → Ca-EDTA + CO2
We can see that the stoichiometric ratio between CaCO3 (in moles) and EDTA (in moles) is 1:1.
Therefore, the number of moles of EDTA used in the titration can be calculated as:
Moles of EDTA = Moles of CaCO3
Moles of EDTA = 0.0049 mol (from Step 1)
Now, we can find the molarity (M) of the EDTA solution by dividing the number of moles of EDTA by the volume of the EDTA solution used in the titration.
Molarity of EDTA = Moles of EDTA / Volume of EDTA solution (in L)
Volume of EDTA solution = 35.18 mL = 35.18 / 1000 L (since 1 L = 1000 mL)
Molarity of EDTA = 0.0049 mol / (35.18 / 1000 L)
Simplifying, we find:
Molarity of EDTA ≈ 0.139 M
So, the molarity of the EDTA solution is approximately 0.139 M.
Step 2: Calculate the number of moles of calcium ions reacted with EDTA.
From the balanced chemical equation, we can see that the reaction between EDTA and calcium ions has a 1:1 stoichiometry. That means one mole of calcium ions reacts with one mole of EDTA.
Since 35.18 mL of the EDTA solution was required for the titration, we can use the equation Molarity = Moles / Volume to calculate the number of moles of EDTA used.
Molarity of EDTA = Moles of EDTA / Volume of EDTA
We already know the volume of EDTA (35.18 mL), so we need to calculate the number of moles of EDTA.
Using the stoichiometry of the reaction, we can say that:
Moles of Ca2+ = Moles of EDTA.
So the number of moles of Ca2+ can be calculated as 0.0049 mol.
Thus, the molarity of EDTA can be calculated as:
Molarity = Moles / Volume
= 0.0049 mol / 35.18 mL
= (0.0049 mol / 0.03518 L) / (1 L / 1000 mL)
= 0.139 mol/L or 0.139 M.
Therefore, the molarity of the EDTA solution is 0.139 M.
Step 2: Calculation of moles of EDTA used in the titration
To determine the molarity of the EDTA solution, we need to find the moles of EDTA used in the titration.
From the balanced chemical equation, we know that 1 mole of EDTA reacts with 1 mole of CaCO3.
Given that 35.18 mL of EDTA solution were required for the titration, we can calculate the moles of EDTA used.
To do this, we need to convert the volume (in milliliters) to liters and then use the known molarity of the EDTA solution.
Moles of EDTA = (Volume of EDTA solution in liters) x (Molarity of EDTA solution)
To convert the volume from milliliters to liters, divide it by 1000:
Volume of EDTA solution = 35.18 mL / 1000 mL/L
= 0.03518 L
Now we can substitute the values into the formula:
Moles of EDTA = (0.03518 L) x (Molarity of EDTA)
So our equation becomes:
0.0049 mol (moles of CaCO3) = 0.03518 L (Volume of EDTA solution) x Molarity of EDTA
Rearranging the equation to solve for the Molarity of EDTA:
Molarity of EDTA = 0.0049 mol / 0.03518 L
Solve this equation to find the molarity of the EDTA solution.