Can someone make sure that I am correct with my first solution? Also I need help with the 2nd problem. I am a little confused about where to begin.
1.) 1.7423g of potassium dichromate were placed in a 250.00 mL volumetric flask and water was added to the mark. Calculate the molarity of the dichromate solution to the appropriate number of significant figures.
0.0237M ?? is this correct
2.) a 1.2523 g sample of a souluble iron(II) salt was dissolved in water and titrated with the dichromate solution prepared in question #1. 37.50mL of the dichromate solution was required to reach the end point.
a.) calculate the mass in grams of iron in the sample.
b.) Calculate the percent of iron in the sample.
The molarity of the dichromate appears to be correct; however, you have 5 significant figures in both the mass and the volume. You need to carry out the division to 5 s.f.
For #2:
1. Write the equation for the titration of iron(II) with dichromate and balance it.
2. Calculate the mols of dichromate used. M x L = mols.
3. Convert mols dichromate in step 2 to mols iron(II) using the coefficients in the balanced equation.
4. Convert mols iron to grams iron.
5. Calculate percent iron.
%Fe = [mass iron step 4/mass sample in the problem]*100 = ??
My balanced answer is
6Fe + Cr2O7 + 14H ---> 6Fe + 2Cr + 7H2O
for mols of dichromate i got 0.00088834
but what would be my conversion factor for part 3?
For question #1, you want to calculate the molarity of the potassium dichromate solution. To do this, you need to know the number of moles of potassium dichromate and the volume of the solution.
Here's how to calculate it:
1. Convert the mass of potassium dichromate to moles by dividing it by its molar mass. The molar mass of K2Cr2O7 (potassium dichromate) is 294.19 g/mol. So, you divide 1.7423 g by 294.19 g/mol to get the number of moles.
2. Calculate the volume of the solution in liters. The given volume is 250.00 mL, so you divide it by 1000 to convert it to liters.
3. Finally, divide the number of moles of potassium dichromate by the volume of the solution to get the molarity. Make sure to round your answer to the appropriate number of significant figures.
For question #2a, you want to calculate the mass of iron in the sample. This can be done using the stoichiometry of the reaction between the iron(II) salt and potassium dichromate.
1. First, calculate the number of moles of potassium dichromate used in the titration. Since the volume of the dichromate solution required to reach the end point is given as 37.50 mL, you can use the molarity from question #1 to calculate the number of moles.
2. The balanced equation for the reaction between potassium dichromate and iron(II) salt is:
K2Cr2O7 + 6 FeSO4 + 7 H2SO4 → Cr2(SO4)3 + 3 SO2 + K2SO4 + 6 Fe2(SO4)3 + 7 H2O
According to the equation, the ratio between the moles of potassium dichromate and moles of iron(II) salt is 1:6. So, multiply the number of moles of potassium dichromate by this ratio to get the number of moles of iron(II) salt.
3. Finally, calculate the mass of iron by multiplying the number of moles of iron(II) salt by its molar mass, which you can find using the periodic table.
For question #2b, you want to calculate the percent of iron in the sample. To do this, divide the mass of iron calculated from question #2a by the initial mass of the sample (1.2523 g) and multiply by 100 to get the percentage.