Question

1) What is the correct net ionic equation, including all coefficients, charges, and phases, for the following set of reactants? Assume that the contribution of protons from H2SO4 is near 100 %.

Ba(OH)2(aq)+H2SO4(aq) --->

Express your answer as a chemical equation.


2) In an ion, the sum of the oxidation states is equal to the overall ionic charge. Note that the sign of the oxidation states and the number of atoms associated with each oxidation state must be considered. In OH-, for example, the oxygen atom has an oxidation state of 2 and the hydrogen atom has an oxidation state of +1, for a total of ( -2 ) + ( +1 ) = -1

(i) What is the oxidation state of each individual carbon atom in C2O4 2^-
Express the oxidation state numerically (e.g., +1).



(ii) Which element is reduced in this reaction?
2HCl+ 2KMnO4 + 3H2C2O4 ? 6CO2 +2MnO2 + 2KCl + 4H2O

Enter the elemental symbol.

Answer 1

Concepts and reason

This problem is based on writing ionic equations and determining oxidation states of elements.

In order to write the complete ionic equation, first write the balanced molecular equation. Then show the aqueous compounds dissociated into ions. Insoluble salts, weak acids and bases are written in form of their molecular formula.

Then cancel out the ions that are common on both the sides to get the net ionic equation.

Fundamentals

Ionic equations are chemical equations in which the electrolytes that dissociate completely in aqueous solution are written as dissociated ions. The symbol aq is written in front of the ions to show that they are in aqueous solutions.

The oxidation state or the oxidation number of an element is equal to the number of electrons that an atom gains, loses or shares when combines with other atoms to form a compound.

To determine the oxidation state of an element there are certain points to remember.

Oxidation state of an uncombined atom is 0. The sum of oxidation states of all atoms in a neutral compound is 0 and in an ion is equal to the ionic charge. In an oxidation reduction reaction if the oxidation number of an element increases, then it shows that is oxidized, and if the oxidation number decreases, it shows that the element is reduced.

(1)

In the reaction, consists of and , consists of and .

In this reaction there is double displacement of ions. So, and forms and and forms water. So, the chemical equation for this reaction is as follows:

In this equation, and are balanced, but there are two and two on left side, and only two hydrogen and one oxygen atoms on right hand side.

So, put the coefficient two before to get the balanced molecular equation as follows:

In the reaction,

Barium hydroxide and sulphuric acid are soluble in water,and barium sulphate is a solid that is insoluble.Water is in liquid state.

Thus the complete chemical equation with physical states of the substances is

In this chemical equation, barium hydroxide and sulphuric acid are aqueous.

So replacing these by their dissociated ions in the chemical equation,we get the complete ionic equation.

As there are no common ions on the two sides, the complete ionic equation is the net ionic equation.

Thus, the net ionic equation is as follows:

(2.i)

The sum of oxidation states of all atoms in an ion is equal to the ionic charge. In ,the charge on ion is . In ,there are two carbons and four oxygen atoms. Oxidation state of oxygen is

Thus, oxidation state is calculated as follows:

Thus, oxidation state of carbon is in .

(2.ii)

Oxidation state of is and Oxidation state of is . and are neutral.

Thus for , the oxidation state is calculated as follows:

For , the oxidation state is calculated as follows:

Thus oxidation state of decreases from in to in.

Ans: Part 1

The net ionic equation is as follows:

Part 2.i

The oxidation state of carbon is in .

Part 2.ii

The is reduced in the reaction.