Consider the reaction: CH3COOH(aq)+H2O(l)⇌H3O+(aq)+CH3COO− (aq) K=1.8×10−5 at 25∘C Part A If a solution initially contains 0.265 molL−1 CH3COOH, what is the equilibrium concentration of H3O+ at 25∘C?

Explanation:

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In this case, for the given ionization chemical reaction of acetic, the equilibrium expression is:

Since aqueous species are considered only. Next, by introducing the reaction extent based on the ICE table, in which it equals the concentration of both H3O+ and CH3COO-, we can also write:

As the acid ionization constant is small in comparison to 0.265 M, we can make an approximation to compute as shown below:

It means that the concentration of H3O+ is:

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it means there are 3 atoms of oxygen

the correct answer would be d. hope this !