Chlorine water on standing loses its color and forms:

Chlorine water is a solution of chlorine gas ($$Cl_2$$) in water. Chlorine gas has a pale yellow-green color, which gives chlorine water its characteristic color. When chlorine water stands, it undergoes a reaction with water.

The reaction between chlorine and water is:

Here, $$Cl_2$$ reacts with $$H_2O$$ to form hydrochloric acid (HCl) and hypochlorous acid (HOCl). Both HCl and HOCl are colorless. As the reaction proceeds, the yellow-green color of chlorine fades because $$Cl_2$$ is consumed, and the products are colorless. This explains why chlorine water loses its color on standing.

Now, examining the options:

Option A suggests HOCl and $$HOCl_2$$. However, $$HOCl_2$$ is not a stable compound and does not form in this reaction. Chlorine water does not produce $$HOCl_2$$.

Option B suggests HCl only. While HCl is formed, hypochlorous acid (HOCl) is also produced, so this option is incomplete.

Option C suggests HCl and $$HClO_2$$ (chlorous acid). Chlorous acid is not a product of chlorine water decomposition. It forms in other reactions, like with chlorine dioxide, not here.

Option D suggests HCl and HOCl. This matches the products of the reaction: hydrochloric acid and hypochlorous acid.

Although hypochlorous acid (HOCl) can decompose slowly over time, especially in light, to form HCl and oxygen ($$2HOCl \rightarrow 2HCl + O_2$$), the question specifies "on standing" without mentioning light. The initial and primary reaction responsible for the loss of color is the formation of HCl and HOCl. Under normal standing conditions, HOCl remains present for a significant period, and the solution contains both HCl and HOCl.

Hence, the correct answer is Option D.