Calculate the oxidation number of sulphur, chromium and nitrogen in H2SO5, Cr2O72– and NO3 –. Suggest structure of these compounds. Count for the fallacy ?

To determine the oxidation numbers of sulfur, chromium, and nitrogen in the compounds H2SO5, Cr2O7^2–, and NO3^–, we need to analyze the chemical structures and apply some rules regarding oxidation states. Let’s break this down step by step for each compound.

Oxidation Number of Sulfur in H2SO5

In H2SO5 (peroxymonosulfuric acid), we can assign oxidation numbers based on the known oxidation states of hydrogen and oxygen. Hydrogen typically has an oxidation state of +1, and oxygen usually has an oxidation state of -2. However, in peroxides, oxygen can have an oxidation state of -1.

• Let’s denote the oxidation state of sulfur as x.
• There are 2 hydrogen atoms contributing +2 to the overall charge.
• There are 5 oxygen atoms. Four of these are in the peroxide form (each -1), and one is in the usual -2 state.

The equation for the oxidation states becomes:

2 (from H) + x (from S) + 4(-1) + (-2) = 0

Solving this gives:

2 + x - 4 - 2 = 0

x - 4 = 0

x = +4

Thus, the oxidation number of sulfur in H2SO5 is +6.

Oxidation Number of Chromium in Cr2O7^2–

Next, let’s look at the dichromate ion, Cr2O7^2–. In this ion, we again use the known oxidation states of oxygen, which is -2.

• Let’s denote the oxidation state of chromium as y.
• There are 7 oxygen atoms contributing a total of 7(-2) = -14.

The equation for the oxidation states becomes:

2y + 7(-2) = -2

2y - 14 = -2

2y = 12

y = +6

Therefore, the oxidation number of chromium in Cr2O7^2– is +6.

Oxidation Number of Nitrogen in NO3^–

Finally, let’s determine the oxidation state of nitrogen in the nitrate ion, NO3^–. Here, we again use the known oxidation state of oxygen.

• Let’s denote the oxidation state of nitrogen as z.
• There are 3 oxygen atoms contributing a total of 3(-2) = -6.

The equation for the oxidation states becomes:

z + 3(-2) = -1

z - 6 = -1

z = +5

Thus, the oxidation number of nitrogen in NO3^– is +5.

Structures of the Compounds

Now, let’s briefly discuss the structures of these compounds:

• H2SO5: This compound has a structure where sulfur is bonded to four oxygen atoms in a tetrahedral arrangement, with one of the oxygen atoms forming a peroxide bond with another oxygen atom.
• Cr2O7^2–: The dichromate ion has a structure where two chromium atoms are connected by bridging oxygen atoms, and each chromium is surrounded by four oxygen atoms in a distorted octahedral geometry.
• NO3^–: The nitrate ion has a trigonal planar structure with nitrogen at the center bonded to three oxygen atoms, one of which carries a negative charge, resulting in resonance structures.

Addressing the Fallacy

In this context, a common misconception might arise from assuming that the oxidation states can be derived without considering the overall charge of the molecule or ion. It’s crucial to remember that the sum of oxidation states must equal the total charge of the compound. This principle is fundamental in accurately determining oxidation states and understanding the chemical behavior of these compounds.

In summary, the oxidation numbers are as follows: sulfur in H2SO5 is +6, chromium in Cr2O7^2– is +6, and nitrogen in NO3^– is +5. Each compound has a distinct structure that reflects its chemical properties and reactivity.