2.) If you pass 10.0mL of a 50.0mL solution of [Co(en)2Cl2]Cl that has been reduced with Zn through a cation exchange column, you will obtain a solution that has three H+ ions for every Co3+ ion that was originally present in the sample. These H+ ions are titrated with 0.10-M NaOH solution. It is found that 20.0mL of NaOH are required. What mass of complex does this correspond to in the 50.0mL?

You lose me here. Which complex are you talking about? The one passed through the column I suppose? What is that complex. At any rate, g complex in this solution is grams = mols x molar mass

To find the mass of the complex in the 50.0mL solution, we need to use the given information about the cation exchange and titration with NaOH.

First, let's determine the molarity of H+ ions in the solution. Since "three H+ ions for every Co3+ ion" are present, the molarity of H+ ions is 3 times the molarity of Co3+ ions.

Given that you passed 10.0mL of the 50.0mL solution through the cation exchange column, you can calculate the moles of Co3+ ions present in that portion.

Moles of Co3+ ions = (volume of solution passed through the cation exchange column) x (molarity of Co3+ ions)

Moles of Co3+ ions = (10.0 mL / 1000 mL/L) x (molarity of Co3+ ions)

Next, since the molarity of H+ ions is three times the molarity of Co3+ ions, you can calculate the moles of H+ ions.

Moles of H+ ions = 3 x (moles of Co3+ ions)

Now, let's determine the moles of NaOH used in the titration. From the titration, we know that 20.0mL of 0.10-M NaOH solution were required.

Moles of NaOH = (volume of NaOH solution used) x (molarity of NaOH solution)

Moles of NaOH = (20.0 mL / 1000 mL/L) x (0.10 mol/L)

Then, we can set up the stoichiometric ratio between H+ ions and NaOH, which is 1:1. This means that moles of H+ ions equal moles of NaOH.

Now, equate the moles of H+ ions to the moles of NaOH to find the moles of Co3+ ions.

3 x (moles of Co3+ ions) = (moles of NaOH)

Finally, calculate the mass of the complex in the original 50.0mL solution.

Mass of complex = (moles of Co3+ ions) x (Molar mass of [Co(en)2Cl2]Cl)

Remember to consult the periodic table for the molar mass of the complex.