Chemical and Ionic Equilibrium - Result Question 15

15. The species present in solution when $CO _2$ is dissolved in water are

(2006 Main)

(a) $CO _2, H _2 CO _3, HCO _3^{-}, CO _3^{2-}$

(b) $H _2 CO _3, CO _3^{2-}$

(c) $HCO _3^{-}, CO _3^{2-}$

(d) $CO _2, H _2 CO _3$

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Answer:

Correct Answer: 15. (a)

Solution:

  1. When $CO _2$ is dissolved in water, following equilibria are established:

$ \begin{aligned} H _2 O+CO _2 & \rightleftharpoons H _2 CO _3 \\ H _2 CO _3 & \rightleftharpoons H^{+}+HCO _3^{-} \\ HCO _3^{-} & \rightleftharpoons H^{+}+CO _3^{2-} \end{aligned} $

Therefore, in solution, all of the above mentioned species exist.