Question

can someone explain the stoichiometry going on here...
so the questions is: A solution containing 0.20g of calcium salt is passed through a column containing the hydrogen form of a strong acid cation exchange resin. The resulting solution is neutralized with 35 mL of .1 M NaOH. What is the # of moles of Calcium2+ per gram of calcium salt.

So here was my thinking, whilst trying to set up an equation.

CaCl2 + HCl --> Ca2+ + 2Cl
Ca2+ + 2Cl +NaOH --> Ca(OH)2 +2NaCl

M=mol/L
mol=M/L
mol=(35mL)(0.1 mol/L) / (1000mL) (0.20)

but the answer has is 35*0.1/1000*0.2*2

where does the 2 come from! lol

Answer 1

Ca^2+ + 2Hresin ==> 2H^+ + Ca(resin)2

Then H^+ + NaOH ==> H2O + Na^+

mols H^+ = M x L = (35/1000) x 0.1
mols Ca^2+ = 1/2 mols H^+ or
(35/1000)x 1/2
mols Ca^2+ per gram =
(35/1000) x 1/2 x 1/0.2 = ?