In which compound does chlorine exhibit valency VII? 1) HClO 2) ZnCl2 3) NaClO3 4) HClO4

Of the listed compounds, the valence of chlorine is VII (oxidation state +7) only in HClO4. This is easily verified as follows:

Valence H = I (oxidation state +1),

the valence Cl is denoted by the unknown x,

valence O = II (oxidation state -2).

Then: 1 + x – 2 * 4 = 0,

hence x = 7.

Similarly, you can calculate the valence of chlorine in other compounds and make sure that it is not equal to VII.

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