Question

Indicate whether each of the following statements is true or false (a) ${\mathrm{H}}_2(g)$ and ${\mathrm{D}}_2(g)$ are allotropic forms of hydrogen. (b) ${\mathrm{ClF}}_3$ is an interhalogen compound. (c) MgO(s) is an acidic anhydride. (d) ${\mathrm{SO}}_2(g)$ is an acidic anhydride. (e) $2{\mathrm{H}}_3{\mathrm{PO}}_4(l)\to {\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_7(l)+{\mathrm{H}}_2\mathrm{O}(g)$ is an example of a condensation reaction. (f) Tritium is an isotope of the element hydrogen. (g) $2{\mathrm{SO}}_2(g)+{\mathrm{O}}_2(g)\to 2{\mathrm{SO}}_3(g)$ is an example of a disproportionation reaction.

Short answer

(a) False (b) True (c) False (d) True (e) True (f) True (g) False

Step-by-step solution

(a) Statement

${\mathrm{H}}_2(g)$ and ${\mathrm{D}}_2(g)$ are allotropic forms of hydrogen. Allotropes are different forms of the same element in the same physical state. ${\mathrm{H}}_2(g)$ stands for diatomic hydrogen gas, and ${\mathrm{D}}_2(g)$ stands for diatomic deuterium gas. Deuterium is an isotope of hydrogen, not an allotrope. Therefore, this statement is false.

(b) Statement

${\mathrm{ClF}}_3$ is an interhalogen compound. Interhalogen compounds are compounds that consist of two or more different halogen elements. In this compound, we have chlorine (Cl) and fluorine (F) - both halogens. Thus, this statement is true.

(c) Statement

MgO(s) is an acidic anhydride. An acidic anhydride is a non-metal oxide that forms an acid when reacted with water. MgO is a metal oxide (magnesium oxide), and, therefore, this statement is false.

(d) Statement

${\mathrm{SO}}_2(g)$ is an acidic anhydride. Sulfur dioxide, ${\mathrm{SO}}_2(g)$, is a non-metal oxide, and when it reacts with water, it forms H2SO3, which is an acid. Therefore, this statement is true.

(e) Statement

$2{\mathrm{H}}_3{\mathrm{PO}}_4(l)\to {\mathrm{H}}_4{\mathrm{P}}_2{\mathrm{O}}_7(l)+{\mathrm{H}}_2\mathrm{O}(g)$ is an example of a condensation reaction. A condensation reaction is a chemical reaction in which two molecules combine, producing a larger molecule and a water molecule as a byproduct. In this case, two molecules of phosphoric acid are combining to form pyrophosphoric acid and water, which fits the definition of a condensation reaction. Therefore, this statement is true.

(f) Statement

Tritium is an isotope of the element hydrogen. Tritium is indeed an isotope of hydrogen. While protium is present in most hydrogen atoms with just one proton, tritium is much rarer and has one proton and two neutrons in its nucleus. Therefore, this statement is true.

(g) Statement

$2{\mathrm{SO}}_2(g)+{\mathrm{O}}_2(g)\to 2{\mathrm{SO}}_3(g)$ is an example of a disproportionation reaction. A disproportionation reaction is a redox reaction in which an element in one oxidation state is simultaneously oxidized and reduced. In this reaction, sulfur in ${\mathrm{SO}}_2(g)$ is in the +4 oxidation state and is oxidized to the +6 oxidation state in ${\mathrm{SO}}_3(g)$. Oxygen in ${\mathrm{O}}_2(g)$ is reduced from the 0 oxidation state to the -2 oxidation state in ${\mathrm{SO}}_3(g)$. Since no element is both oxidized and reduced, this statement is false.

Key concepts

Allotropes and Isotopes

Allotropes are different structural forms of the same element in the same physical state, such as carbon existing as graphite, diamond, and graphene. Isotopes, on the other hand, are atoms of the same element that have different numbers of neutrons and thus different mass numbers. For example, hydrogen has three isotopes: protium with no neutrons, deuterium with one neutron, and tritium with two neutrons.

The confusion between allotropes and isotopes often arises because both terms refer to forms of an element. However, allotropy pertains to different molecular structures, such as O2 and O3 (ozone), which are both oxygen allotropes, while isotopy describes variations in atomic nuclei.

Interhalogen Compounds

Interhalogen compounds consist of halogens, which are the elements found in Group 17 of the periodic table. These compounds are formed between two or more different halogens, and the general formula is (XY_n), where 'X' and 'Y' are different halogens, and 'n' can be 1, 3, 5, or 7. Examples of interhalogen compounds include chlorine trifluoride (ClF3) and bromine monochloride (BrCl). The properties of interhalogens are intermediate between those of the parent halogens, and they are typically more reactive than the diatomic halogen molecules.

Acidic and Basic Anhydrides

Acidic anhydrides, also known as acid oxides, are non-metal oxides that react with water to form an acid. For example, sulfur dioxide (SO2) reacts with water to produce sulfurous acid (H2SO3). On the contrary, basic anhydrides, or basic oxides, are metal oxides that react with water to produce a base, such as magnesium oxide (MgO) that reacts with water to form magnesium hydroxide (Mg(OH)2).

It is essential to recognize these two types of anhydrides as the naming can seem complex due to the term 'anhydride,' which means 'without water.' Acidic anhydrides are related to non-metals and their capacity to form acids upon hydration, while basic anhydrides pertain to metals and their ability to form bases.

Condensation Reactions

Condensation reactions are a class of reactions where two or more molecules combine, usually with the elimination of a small molecule such as water, to form a larger molecule. These reactions are commonly seen in the formation of polymers, where monomer units join to create long chains. An example includes the synthesis of nylon from adipic acid and hexamethylene diamine, releasing water in the process.

Understanding the concept of condensation reactions is critical, as they are vital in various biological and industrial synthesis processes. These reactions contribute to the complex structure of proteins and nucleic acids vital in life processes.

Disproportionation Reactions

Disproportionation reactions represent a specific type of redox reaction where a single element undergoes both oxidation and reduction, forming two different products with different oxidation states. A classic example of disproportionation is the reaction of chlorine with water, forming hydrochloric acid (HCl) and hypochlorous acid (HClO), where chlorine is both reduced and oxidized.

Recognizing disproportionation is important because it helps to understand redox balance and its impact on reaction direction. These reactions are prevalent in biochemistry and industrial processes, such as the use of hydrogen peroxide by enzymes like catalase.

Chemical Nomenclature

Chemical nomenclature is the systematic naming of chemical compounds based on their structure and composition. It follows specific rules set by the International Union of Pure and Applied Chemistry (IUPAC). The proper naming of compounds includes identifying functional groups, the longest carbon chain, and the positions of substituents or functional groups on that chain.

For instance, in organic chemistry, alcohols end with '-ol,' while acids end with '-oic acid.' Learning these naming conventions is pivotal for clear communication in chemistry and for understanding the properties and reactions of compounds based on their names.

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, are chemical processes where electrons are transferred between two species. Reduction pertains to the gain of electrons, leading to a decrease in oxidation number, while oxidation involves the loss of electrons, leading to an increase in oxidation number. A widespread example is the rusting of iron, where iron (Fe) is oxidized by oxygen (O2) from the air.

In the context of the initial statement, the reaction of sulfur dioxide with oxygen to form sulfur trioxide does not constitute a disproportionation reaction because sulfur does not undergo simultaneous oxidation and reduction; rather, it is a straightforward redox reaction where sulfur is only oxidized.