Problem 138 - A Complete Resource Book in Chemistry for JEE Main

Question

Select the incorrect statement: (a) Fluorine cannot show oxidation number greater than zero (b) Halogens do not directly combine with oxygen (c) Iodine can not displace chlorine from \(\mathrm{KClO}_{3}\) (d) Euchlorine is a mixture of \(\mathrm{Cl}_{2}\) and \(\mathrm{Cl}_{2} \mathrm{O}_{7}\)

Step-by-Step Solution

Answer

The incorrect statement is (d).

Step 1: Evaluate Statement (a)

Fluorine is the most electronegative element and always shows an oxidation number of -1 in compounds because it does not form compounds with positive oxidation states. Therefore, statement (a) which says "Fluorine cannot show oxidation number greater than zero" is correct.

Step 2: Evaluate Statement (b)

Halogens like chlorine, bromine, and iodine can combine with oxygen to form oxides. However, these combinations are generally not direct, and special conditions are often necessary. So, statement (b) "Halogens do not directly combine with oxygen" is largely considered incorrect due to the possibility of formation under specific conditions.

Step 3: Evaluate Statement (c)

Iodine is less reactive than chlorine and cannot displace chlorine from its compounds such as potassium chlorate (\(\mathrm{KClO}_{3}\)). Therefore, statement (c), "Iodine can not displace chlorine from \(\mathrm{KClO}_{3}\)," is correct.

Step 4: Evaluate Statement (d)

Euchlorine is actually a mixture of chlorine gas (\(\mathrm{Cl}_{2}\)) with chlorine peroxide (\(\mathrm{ClO}_{2}\)), not \(\mathrm{Cl}_{2} \mathrm{O}_{7}\). Thus, statement (d) is incorrect.

Key Concepts

Fluorine properties

Fluorine is an exceptional element, often characterized by its high electronegativity. Electronegativity refers to an atom's ability to attract and hold onto electron pairs. In the periodic table, fluorine is at the top of the halogen group, making it the most electronegative of all elements. Due to this pronounced electronegativity, fluorine almost always forms compounds where it has an oxidation number of -1. This is because it tends to attract electrons strongly to itself, rarely giving them away to attain a positive oxidation state. In its interactions with other elements, fluorine usually acts as an oxidizing agent, prompting other atoms to lose electrons, while it gains electrons. When discussing fluorine properties, it's vital to remember that it never naturally assumes a positive oxidation state in compounds.

Halogen oxides

Halogens such as chlorine, bromine, and iodine can combine with oxygen to form varied oxides, though not through direct synthesis. These oxides are created under particular reaction conditions. Halogen oxides bear importance because of their diverse chemical behaviors and applications.

• Chlorine can form oxides like chlorine monoxide (0Cl_2O0) and others, dependent on specific reaction conditions.
• Similarly, iodine can form solid iodine pentoxide (0I_2O_50) under specialized conditions.

These halogen oxides typically demonstrate unique reactivity and may even serve as intermediates in various chemical reactions or industrial processes. They are crucial in illustrating the versatility and the non-direct way halogens interact with oxygen.

Reactivity series

In chemistry, the reactivity series is a list of elements ordered by their reactivity. Within this series, elements are compared based on their ability to displace others in compounds. When considering halogens like chlorine, bromine, and iodine, the reactivity decreases as you move down the group.

• Chlorine is more reactive than iodine. Because of this, it can displace iodine from its salts or other compounds.
• Conversely, iodine is unable to displace chlorine due to its lower reactivity.

The concept of the reactivity series is fundamental in predicting how halogens will behave in displacement reactions, just as the one involving potassium chlorate (0KClO_30), where iodine cannot replace chlorine.

Euchlorine composition

Euchlorine might sound complex, but it's essentially a mixture known for containing chlorine gas (0Cl_20) and chlorine dioxide (0ClO_20). This mixture should not be confused with compounds involving chlorine heptoxide. Products arising from these mixes, especially 0ClO_20, are characterized by robust oxidizing capabilities beneficial in various industrial applications, including water treatment and bleaching processes. Understanding the correct composition of euchlorine is vital as it emphasizes the subtle, yet important differences between chlorine compounds. Misinterpreting it could lead to errors in chemical application or processes. Thus, recognizing euchlorine's proper makeup is critical in practical and academic settings.