Why are chemical equilibria called dynamic equilibria?

Because molecules are moving so they change from reactants to products and vice versa.

Explanation:

Hello,

In this case, it is widely known that chemical equilibrium is related with such condition at which the rate of consumption of reactants and formation of products tends to zero so their concentrations remain the same over the time. For instance, if we consider the formation of hydrogen chloride at equilibrium:

We can also see that the reactants, hydrogen and chlorine are consumed to form hydrogen chloride and it also goes back to its reactants in a dynamic equilibrium (because they are constantly changing).

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answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.