Calculating concentration in molar units?

Question

What is the concentration in Molar units of sulfate ions present in 67.2 mL of 0.286 M solution of K2SO4 mixed with 59.9 mL of 0.345 M solution of Na2SO4?

Please help me solve this problem and show the steps to take in solving it. Thanks

Answer 1

0.286 molar K2SO4 has 0.286 moles of sulfate ions in 1 liter. However, one has only 67.2 ml, and since there are 1000 ml in a liter, this means one has 67.2/1000 liters, or 0.067 liters. So, 0.286 moles/liter times 0.067 liters yields 0.02 moles from the K2SO4. Repeat the same with the Na2SO4 and one gets 59.9/1000 times 0.345 = 0.02 moles. (Do you sence a pattern here?). The answer of course is the total number of moles of sulfate ions, or 0.02 + 0.02 = 0.04 moles.

Answer 2

Both of these salts will fully ionize and you will get 1 mole of sulfate ions for every mole of total salts.

So add the moles of salt together

for the K2SO4 it is (0.0672 L)(0.286 moles / Liter)
for the Na2SO4 it is (0.0599 L)(0.345 moles /liter)

Just multiply and add