# chemistry question please help?

if you pass 10ml of a 50ml 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 20.5ml of NaOH are required

a.) How many moles of NaOH are used?

b.) How many moles of Co3+ does this correspond to?

c.) How many moles of the complex must have originally been present in the 50.0mL?

d.) What mass of complex does this correspond to in the 50.0mL?

e.) Calculate the number of moles of Cl- that are in a 10.00mL sample of the complex.

f.) What volume of .1M AgNO3 solution is required to precipitate all the chloride as AgCl?

### 1 Answer

- hcbiochemLv 73 weeks agoFavorite Answer
a) 0.0205 L X 0.10 mol/L = 2.05X10^-3 mol H+

b) Since 3 H+ correspond to 1 Co3+, 2.05X10^-3 mol H+ X (1 mol Co3+/ 3 mol H+) = 6.83X10^-4 mol Co3+c) In the original 50.0 mL of the solution, there would be 6.83X10^-4 mol X 5 = 3.42X10^-3 mol complex.d) The molar mass of the complex is 285.48 g/mol. So the mass of the complex is:3.42X10^-3 mol X 285.48 g/mol = 0.975 g complex

e) 6.83X10^-4 mol complex X (3 mol Cl / 1 mol complex) = 2.05X10^-3 mol Cl-

f) I'm assuming that the question means all of the chloride in the 10 mL sample as referred to in part e). So,

2.05X10^-3 mol Cl- X (1 mol Ag+ / 1 mol Cl-) X (1 L / 0.10 mol Ag+) = 0.0205 L = 20.5 mL AgNO3 solution