Homework Help: chemistry

Posted by titration on Tuesday, October 7, 2008 at 5:36pm.

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.

chemistry - DrBob222, Tuesday, October 7, 2008 at 5:49pm
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.
chemistry - DrBob222, Tuesday, October 7, 2008 at 5:55pm
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 = ??
chemistry - titration, Thursday, October 9, 2008 at 12:25am
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?

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