What are the concentrations of [K+], [OH-], [CO32-] and [H+], in a 1.2 M solution of K2CO3 ? (Note: Question is asking for concentrations and not pH) g

The concentrations are: [K⁺] = 1.2 M, [OH⁻] = 0.016 M, [CO₃²⁻] = 1.18 M and [H⁺] = 6.25x10⁻¹³ M.

Explanation:

The dissociation equation of K₂CO₃ in water is:

K₂CO₃(aq) ⇄  K⁺(aq) + CO₃²⁻(aq)     (1)

Also, the CO₃²⁻ will react with water as follows:

CO₃²⁻(aq) + H₂O(l) ⇄ HCO₃⁻(aq) + OH⁻(aq)    (2)

The constant of the reaction (2) is:    

The solution of K₂CO₃ is 1.2 M, and since the mole ratio of K₂CO₃ with K⁺ and CO₃²⁻ is 1:1, then we have:                      

Now, from equation (2) we have:

CO₃²⁻(aq) + H₂O(l) ⇄ HCO₃⁻(aq) + OH⁻(aq)    (3)

1.2 - x                                x               x

   (4)  

By solving equation (4) for x we have:

x = 0.016 M = [HCO₃⁻] = [OH⁻]        

Hence, the CO₃²⁻ concentration is:                        

[CO₃²⁻] = 1.2 M - 0.016 M = 1.18 M

Finally, the concentration of [H⁺] is:

Therefore, the concentrations are: [K⁺] = 1.2 M, [OH⁻] = 0.016 M, [CO₃²⁻] = 1.18 M and [H⁺] = 6.25x10⁻¹³ M.

I hope it helps you!

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