Problem 65 - Chemistry Central Science

Question

Chlorine reacts with oxygen to form \(\mathrm{Cl}_{2} \mathrm{O}_{7} .\) (a) What is the name of this product (see Table 2.6)? (b) Write a balanced equation for the formation of \(\mathrm{Cl}_{2} \mathrm{O}_{7}(l)\) from the elements. (c) Under usual conditions, \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) is a colorless liquid with a boiling point of \(81^{\circ} \mathrm{C}\). Is this boiling point expected or surprising? (d) Would you expect \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) to be more reactive toward \(\mathrm{H}^{+}(a q)\) or \(\mathrm{OH}^{-}(a q) ?\) Explain.

Step-by-Step Solution

Answer

(a) The name of the product \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) is Dichlorine heptoxide. (b) The balanced equation for its formation is \(2\,\mathrm{Cl}_2 + 7\,\mathrm{O}_2 \rightarrow 2\,\mathrm{Cl}_{2} \mathrm{O}_{7}\). (c) The boiling point of \(81^{\circ} \mathrm{C}\) is unexpected due to the strong intermolecular forces present in its structure, but this may be explained by its highly symmetrical and compact shape. (d) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) is more likely to react with \(\mathrm{OH}^{-}(a q)\) as it behaves as an acid due to its electron-deficient nature.

Step 1: (a) Name of the product: \(\mathrm{Cl}_{2} \mathrm{O}_{7}\)

To find the name of this product, first, identify the anion and cation present in the compound. In this case, both elements are nonmetals - chlorine and oxygen. The compound is a covalent molecular substance and so a Roman numeral is not used to indicate the charge. The prefix used in naming covalent molecular substances are: mono, di, tri, tetra, penta, hexa, hepta, octa, nona, and deca. Therefore, the name of \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) is Dichlorine heptoxide.

Step 2: (b) Balanced equation for the formation of \(\mathrm{Cl}_{2} \mathrm{O}_{7}\)

The formation of \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) involves the reaction of chlorine and oxygen, which are the elements needed to form the compound. Write the equation and balance it: \[ \mathrm{Cl}_2 +\mathrm{O}_2 \rightarrow \mathrm{Cl}_{2} \mathrm{O}_{7} \] Now balance the equation by adjusting the coefficients so that the total number of atoms of each element is equal on both sides: \[ 2\,\mathrm{Cl}_2 + 7\,\mathrm{O}_2 \rightarrow 2\,\mathrm{Cl}_{2} \mathrm{O}_{7} \]

Step 3: (c) Boiling point analysis

The boiling point of \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) is \(81^{\circ} \mathrm{C}\). This value is quite unexpected, considering the three oxygen double bonds and one single oxygen bond in its structure. These bonds create strong intermolecular forces, which usually increase the boiling point, but in this case, the boiling point is relatively low. The explanation could be that the compound has a highly symmetrical and compact shape, which reduces the intermolecular forces between its molecules and results in a comparatively low boiling point.

Step 4: (d) Reactivity towards \(\mathrm{H}^{+}(a q)\) and \(\mathrm{OH}^{-}(a q)\)

To answer this question, let's consider the acidic or basic properties of the compound. The chlorine heptoxide contains seven oxygen atoms, which are strongly electronegative and can attract electrons from other atoms, making the compound electron-deficient. Consequently, \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) would be more likely to behave as an acid and react with a base. Since \(\mathrm{OH}^{-}(a q)\) is a base, this suggests that \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) would be more reactive with \(\mathrm{OH}^{-}(a q)\) than with \(\mathrm{H}^{+}(a q)\), which is an acidic ion.

Key Concepts

Naming Chemical Compounds

Understanding the process of naming chemical compounds is vital for students to comprehend the composition and characteristics of different molecules. When it comes to covalent molecular substances, such as dichlorine heptoxide (LaTeX format here), the prefixes used are indicative of the number of atoms present. In this compound, 'di' refers to the two atoms of chlorine and 'hepta' indicates that there are seven oxygen atoms. Consequently, the correct name for LaTeX format here is 'dichlorine heptoxide'.

It's crucial to note that Roman numerals aren't used in these instances because the elements involved are nonmetals and do not form ions with fixed charges as metals do. Instead, the prefixes provide a clear idea of the molecule's structure, thereby contributing to a better understanding of its properties.

Balancing Chemical Equations

The art of balancing chemical equations lies at the heart of chemistry. In the textbook's example, we balance the equation for the formation of dichlorine heptoxide from chlorine and oxygen. By following the Law of Conservation of Mass, we ensure that the number of each type of atom on the reactants side is equal to that on the products side. The balanced equation, LaTeX format here, shows that two molecules of chlorine react with seven molecules of oxygen to form two molecules of dichlorine heptoxide.

This step is crucial for students to master as it provides a foundation for all stoichiometric calculations, which are essential for predicting the outcomes of reactions and understanding the quantitative nature of chemical reactions.

Boiling Point Analysis

Boiling point analysis often surprises students when the observed data don't align with their predictions. For dichlorine heptoxide, the boiling point is unexpectedly low at 81°C, despite the presence of strong oxygen double bonds. The underlying reason for this anomaly is structural: the molecule's symmetrical and compact shape reduces intermolecular forces, leading to a low boiling point.

This example emphasizes the complexity of boiling point determinations, which rely on not just intermolecular forces but also molecular geometry. Recognizing these nuances helps students to predict and rationalize the physical properties of chemical compounds.

Reactivity in Chemistry

Reactivity in chemistry is influenced by the nature of a chemical species and the types of reactions it tends to undergo. Dichlorine heptoxide is an acidic oxide, making it prone to react with bases rather than acids due to its electron-withdrawing oxygen atoms. Thus, LaTeX format here is more reactive toward LaTeX format here (a hydroxide ion), a base, than LaTeX format here (a hydronium ion), an acid. This concept teaches students about the acid-base behavior of compounds and helps to predict reactivity trends, which is particularly useful in understanding chemical interactions in various fields like environmental chemistry and materials science.