1 Ca (s) + 2 HF (aq) → 1 CaF2 (s) +1 H2 (g) Identify the coefficient(s). Identify the subscript(s). What is the state of each of the reactants? What will serve as evidence that a reaction has occurred?

Answer :

The coefficients are, 1 in Ca, 2 in HF, 1 in CaF₂ and 1 in H₂

The subscripts are, 2 in CaF₂ and 2 in H₂

The states of reactants are, Ca in solid state (s) and HF in aqueous state (aq).

The evidence that a reaction occurred is, the new substances are formed in the chemical reaction.

Explanation :

Balanced chemical reaction : It is defined as the reaction in which the number of atoms of individual elements present on reactant side must be equal to the product side.

If the amount of atoms of each type on the left and right sides of a reaction differs then to balance the equation by adding coefficient in the front of the elements or molecule or compound in the chemical equation.

The coefficient tell us about that how many molecules or atoms present in the chemical equation.

Coefficient : It is a number that written in front of the element, molecule or ion.

Subscript : It is a small number that placed slightly lower-right than the normal text.

The given balanced chemical reaction is:

In this reaction:

The coefficients are, 1 in Ca, 2 in HF, 1 in CaF₂ and 1 in H₂

The subscripts are, 2 in CaF₂ and 2 in H₂

The states of reactants are, Ca in solid state (s) and HF in aqueous state (aq).

The evidence that a reaction occurred is, the new substances are formed in the chemical reaction.

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.