What is the total concentration of all ions (the sum of their individual concent

Question

What is the total concentration of all ions (the sum of their individual concentrations) in aqueous solutions of the following? Hint: Each substance is an electrolyte that dissociates in water to produce ions. Use the link table of polyatomic ions if you do not recognize the polyatomic ion. For example, Na2SO4 -> 2Na1+ + SO42- when it dissolves, so a 1 M soln of Na2SO4 is 2M in Na1+ and 1M in SO42- and the total concentration of ions is 2 M + 1 M = 3M.

0.0260-M NaCl M

0.0540-M Na2SO4 M

0.0700-M K2Cr2O7 M

Explanation / Answer

1) 0.0260 M NaCl
NaCl ionizes completely as,
NaCl (aq.) -----------> Na+ (aq.) + Cl- (aq.)

[Na+] = [Cl-] = [NaCl] = 0.0260 M

Total ionic concentration = [Na+] + [Cl-] = 0.0260 + 0.0260 = 0.0520 M

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2) 0.0540 Na2SO4.

Na2SO4.ionizes completely as,

Na2SO4. -----------> 2 Na+ (aq.) + SO42-(aq.)

It's clear that, 1 mole of Na2SO4. gives 2 moles of Na+ and 1 mole of SO42-. i.e. 3 ions per one mole of Na2SO4.

hence,

[Na+] = 2 x [Na2SO4] = 2 x 0.0540 = 0.1080 M

[SO42-] = [Na2SO4] = 0.0540 M

Therefore,

Total ionic concentration = [Na+] + [SO42-] = 0.1080 + 0.0540 = 0.1620 M

OR

Simply we can say,

Total ionic concentration = 3 x [Na2SO4] = 3 x 0.0540 = 0.1620 M

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3) 0.0700 M K2Cr2O7.

K2Cr2O7. (aq.) ---------> 2K+ (aq.) + Cr2O72- (aq.)

It's clear that, 1 mole of K2Cr2O7. gives 2 moles of K+ and 1 mole of Cr2O72-.

Total of 3 ions produced per mole of K2Cr2O7.

Hence,

Total ionic concentration = 3 x [K2Cr2O7.] = 3 x 0.0700 = 0.2100 M

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