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?

To solve this problem, we need to follow the steps given in the question and use the concept of stoichiometry.

Step 1: Calculate the moles of NaOH used.
Since we know the volume and concentration of NaOH used in the titration, we can calculate the moles of NaOH used. The equation for the reaction between NaOH and H+ is:
NaOH + H+ -> Na+ + H2O
From the balanced equation, we can see that 1 mole of NaOH reacts with 1 mole of H+. Therefore, the moles of NaOH used is equal to the moles of H+ in the solution.

moles of NaOH used = (volume of NaOH used in liters) x (concentration of NaOH)
= (20.0 mL) x (0.10 mol/L) / 1000 mL/L
= 0.002 mol

Step 2: Calculate the moles of Co(en)2Cl2 complex in the 10.0 mL solution.
From the given information, we know that for every Co3+ ion present in the sample, there are three H+ ions. Therefore, the moles of Co3+ ions is one-third of the moles of H+ ions.
Since the solution has a volume of 10.0 mL, the moles of Co3+ ions in the solution is:
moles of Co3+ ions = (moles of H+ ions) / 3

To find the moles of H+ ions, we use the moles of NaOH used in Step 1, as discussed above:
moles of H+ ions = moles of NaOH used

Substituting the values, we get:
moles of Co3+ ions = 0.002 mol / 3
= 0.0006667 mol

Step 3: Calculate the mass of complex in the 50.0 mL solution.
To calculate the mass of the complex in the 50.0 mL solution, we need to convert the moles of the complex to grams using its molar mass.

First, we need to find the moles of the complex in 50.0 mL:
moles of complex = (10.0 mL / 50.0 mL) x (0.0006667 mol)
= 0.0001333 mol

Now, we can calculate the mass of the complex using its molar mass. Since the formula of the complex is not given, we cannot provide the exact molar mass. However, if you know the molar mass of the complex, you can multiply it by the moles of the complex to get the mass.

mass of complex = moles of complex x molar mass

Substituting the values, you will get the mass of the complex in grams.
Note: The answer will depend on the molar mass of the complex used.