calculate the normality of a solution prpared by dissolving 220.0 mg of K2Cr2O7 in 100 ml solution that will be used to oxidize ferrous chloride according to the unbalanced reaction.
6FeCl2 + K2Cr2O7 + 14HCl ==>2CrCl3 + 2KCl + 6FeCl3 + 7H2O Check that.
molar mass K2Cr2O7 = 294.184
equivalent weight = 294.184/6 = 49.031
# equivalents K2Cr2O7 = grams/equivalent weight = 0.220 g/49.031 = ??
N = #eq/L. Substitute#equivalents and L and solve.
Why did u divine the molar mass by 6 for the equivalent weight??
To calculate the normality of a solution prepared by dissolving a compound, we need to first determine the number of moles of the compound dissolved and then divide it by the volume of the solution in liters.
In this case, we have:
Mass of K2Cr2O7 = 220.0 mg
Volume of solution = 100 mL
Step 1: Convert the mass of K2Cr2O7 to moles.
To do this, we need to know the molar mass of K2Cr2O7.
The molar mass of K2Cr2O7 = (2 * molar mass of K) + (2 * molar mass of Cr) + (7 * molar mass of O)
= (2 * 39.10 g/mol) + (2 * 52.00 g/mol) + (7 * 16.00 g/mol)
= 294.18 g/mol
Number of moles of K2Cr2O7 = Mass of K2Cr2O7 / Molar mass of K2Cr2O7
= 0.220 g / 294.18 g/mol
≈ 0.000748 mol
Step 2: Convert the volume of the solution to liters.
Given that 1 mL = 0.001 L, we have:
Volume of solution = 100 mL * (0.001 L / 1 mL)
= 0.1 L
Step 3: Calculate the normality of the solution.
Normality (N) is defined as the number of equivalents of a solute per liter of solution. For this reaction, K2Cr2O7 will react as an oxidizing agent donating 6 equivalents of electrons per mole.
Number of equivalents = Number of moles * Number of equivalents per mole
= 0.000748 mol * 6 eq/mol
= 0.00449 eq
Normality (N) = Number of equivalents / Volume of solution
= 0.00449 eq / 0.1 L
= 0.0449 N
Therefore, the normality of the solution prepared by dissolving 220.0 mg of K2Cr2O7 in 100 ml of solution is approximately 0.0449 N.
To calculate the normality of a solution, you need to know the number of equivalents of the solute and the volume of the solution. In this case, we will first determine the number of equivalents of K2Cr2O7 and then use it to calculate the normality.
1. Find the molecular weight of K2Cr2O7:
- K (potassium) has a molar mass of 39.10 g/mol.
- Cr (chromium) has a molar mass of 52.00 g/mol.
- O (oxygen) has a molar mass of 16.00 g/mol.
- Multiply the molar mass of each element by its subscript and sum them up:
(2 x 39.10) + (2 x 52.00) + (7 x 16.00)
The molecular weight of K2Cr2O7 is 294.18 g/mol.
2. Calculate the number of moles of K2Cr2O7:
Divide the mass of K2Cr2O7 by its molar mass:
220.0 mg / 294.18 g/mol = 0.7471 mmol (millimoles)
3. Determine the number of equivalents:
For K2Cr2O7, there are three moles of electrons transferred per mole of K2Cr2O7 molecule in the balanced equation. Therefore, the number of equivalents is also 0.7471 mmol.
**It's important to note that "normality" refers to the number of equivalents of the solute divided by the volume of solution in liters.**
4. Convert the volume of the solution to liters:
100 ml = 0.1 L
5. Calculate the normality:
Normality (N) = Number of equivalents / Volume of solution (in L)
N = 0.7471 mmol / 0.1 L
Therefore, the normality of the solution is 7.471 N.