Consider the standardization of a solution of K2Cr2O7 with iron metal according to the following:
Reaction: Fe + Cr2O7-2 → Fe +3 + Cr+3a.
How many grams of K2Cr2O7 are required to prepare 500 ml of a 0.13 N solution?
What is the exact normality of the solution prepared in part a if 0.1376 g of iron metal were exactly reacted with 48.56 ml of the solution?
0.13N= # of equivalents/500 x10^-3 L, solving for # of equivalents
# of equivalents in 0.13N=(0.13N)(500 x 10^-3L)
# of equivalents in 0.13N= g of solute/49.03g, solve for grams of solute,
(49.03g, solve )*(# of equivalents in 0.13N)= g of solute
I'm not sure if you are asking for the normality of Fe, but if you are use
NV=NV, and solve for N
N=[(500x10^-3 l)(0.13N)]/48.86 x 10^-3 L
N= 1.33N
Hopefully Dr.Bob222 checks this and corrects it if it is wrong.
Cr2O7^2- ==> 2Cr^3+ + 6e
a.
mL x N x m.e.w. = grams.
500 mL x 0.13 x (294.18/6000) = grams = about 3.2 grams K2Cr2O7.
I won't do b for you; Fe doesn't react with Cr2O6^2-. With Fe^2+ yes but not Fe metal.
Okay, my setup was correct then. I just didn't show how I got 43.09g.
B is what I was worried about!!!!!!
To find the grams of K2Cr2O7 required to prepare 500 ml of a 0.13 N solution, we need to use the molar concentration of K2Cr2O7 and convert it to the required units.
Here's how you can do it:
1. Start by calculating the molar concentration (M) of K2Cr2O7:
N is equivalent to the molar concentration (M) multiplied by the number of equivalents (n).
In this case, the normality (N) is given as 0.13 N.
2. Find the molar mass of K2Cr2O7:
K (Potassium) has an atomic mass of 39.10 g/mol.
Cr (Chromium) has an atomic mass of 51.99 g/mol.
O (Oxygen) has an atomic mass of 16.00 g/mol.
Calculate the molar mass of K2Cr2O7 by adding the molar masses of the constituent atoms:
Molar mass = (2 * atomic mass of K) + (2 * atomic mass of Cr) + (7 * atomic mass of O)
3. Convert the normality to molar concentration (M):
N = M * n, where n is the number of equivalents.
In this case, n is equal to the number of electrons transferred in the balanced chemical equation.
From the given balanced equation: Fe + Cr2O7-2 → Fe+3 + Cr+3
We can see that 6 electrons are transferred.
Therefore, n = 6.
Rearrange the above equation and solve for M:
M = N / n
4. Calculate the value of M:
Substitute the given values into the equation:
M = 0.13 N / 6
5. Calculate the amount of K2Cr2O7 required in grams:
The molar concentration (M) is equal to moles per liter (mol/L).
Since we need to prepare 500 ml of the solution, we need to calculate the moles needed for this volume.
Use the equation: moles = M * volume (in liters)
6. Convert moles to grams using the molar mass of K2Cr2O7:
moles = grams / molar mass
So, to find the grams of K2Cr2O7 required:
Step 1: Calculate the molar concentration (M) using the given normality (N) and number of equivalents (n).
Step 2: Find the molar mass of K2Cr2O7.
Step 3: Calculate the value of M using the equation: M = N / n.
Step 4: Calculate the moles needed for 500 ml of the solution using the equation: moles = M * volume (in liters).
Step 5: Convert moles to grams using the molar mass of K2Cr2O7.
For the exact normality of the solution prepared in part a:
You'll need to use stoichiometry to calculate the exact normality of the solution from the amount of iron metal reacted and the volume of the solution used.
Here's how you can do it:
1. Calculate the moles of iron metal reacted:
Convert the mass of iron metal given (0.1376 g) to moles using its molar mass.
2. Use the balanced chemical equation to determine the stoichiometric ratio between iron (Fe) and K2Cr2O7:
From the balanced equation: Fe + Cr2O7-2 → Fe+3 + Cr+3
The stoichiometric ratio is 1:1, meaning that for every 1 mole of Fe reacted, 1 mole of K2Cr2O7 is required.
3. Calculate the moles of K2Cr2O7 required:
Since we know the moles of Fe reacted and the stoichiometric ratio, we can directly calculate the moles of K2Cr2O7 required.
4. Convert the moles of K2Cr2O7 to normality (N):
Normality is defined as the number of equivalents per liter.
In this case, since we're given the volume of the solution used (48.56 ml), we can calculate the normality.
So, to find the exact normality:
Step 1: Calculate the moles of iron metal reacted using its mass and molar mass.
Step 2: Determine the stoichiometric ratio between Fe and K2Cr2O7 from the balanced equation.
Step 3: Calculate the moles of K2Cr2O7 required using the moles of Fe reacted and the stoichiometric ratio.
Step 4: Convert the moles of K2Cr2O7 to normality using the volume of the solution used.