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Chapter 20: Problem 96

Which of following statement(s) is/are true? a. Phosphoric acid is a stronger acid than nitric acid. b. The noble gas with the lowest boiling point is helium. c. Sulfur is found as the free element in the earth's crust. d. One of the atoms in Teflon is fluorine. e. The \(\mathrm{P}_{4}\) molecule has a square planar structure.

Short Answer

Expert verified
Statements b, c, and d are true.

Step by step solution

01

Statement a: Phosphoric acid is a stronger acid than nitric acid.

To verify this statement, let's first examine the formulas and acid dissociation constants (\(\mathrm{K}_{\mathrm{a}}\)) of the two acids. Phosphoric acid is \(\mathrm{H}_{3}\mathrm{PO}_{4}\) with \(\mathrm{K}_{\mathrm{a}1} = 7.3 \times 10^{-3}\), \(\mathrm{K}_{\mathrm{a}2} = 6.2 \times 10^{-8}\), and \(\mathrm{K}_{\mathrm{a}3} = 4.8 \times 10^{-13}\). Nitric acid is \(\mathrm{HNO}_{3}\) with \(\mathrm{K}_{\mathrm{a}} = 25\). A stronger acid has a higher value of \(\mathrm{K}_{\mathrm{a}}\). Since the \(\mathrm{K}_{\mathrm{a}}\) value of nitric acid is higher than any of the \(\mathrm{K}_{\mathrm{a}}\) values of phosphoric acid, nitric acid is stronger than phosphoric acid. Thus, statement a is false.
02

Statement b: The noble gas with the lowest boiling point is helium.

The boiling point of a substance depends on the strength of the forces between its particles. For noble gases, the only forces present are weak van der Waals forces, which are dependent on the size of the atom. As the size of the atom increases, so does the strength of the van der Waals forces, and thus the boiling point. Among noble gases, helium has the smallest atom size, and therefore the weakest van der Waals forces. As a consequence, helium has the lowest boiling point among the noble gases. Therefore, statement b is true.
03

Statement c: Sulfur is found as the free element in the earth's crust.

Sulfur is present in the earth's crust primarily as sulfide and sulfate minerals, such as pyrite, galena, and gypsum. However, it can also be found in its native form, i.e., as the free element, especially around volcanic regions, where underground deposits can be brought to the surface through geothermal activity. Therefore, statement c is true.
04

Statement d: One of the atoms in Teflon is fluorine.

Teflon is a brand name for the polymer polytetrafluoroethylene (PTFE), which consists of a chain of carbon atoms with fluorine atoms attached to each carbon. The formula for PTFE is \(\mathrm{(C}_{2}\mathrm{F}_{4})_{\mathrm{n}}\), where n represents the number of repeating units in the polymer chain. As we can see, fluorine is one of the atoms present in Teflon. Therefore, statement d is true.
05

Statement e: The \(\mathrm{P}_{4}\) molecule has a square planar structure.

The \(\mathrm{P}_{4}\) molecule consists of four phosphorus atoms covalently bonded to one another. The most stable geometry for such a molecule is a tetrahedral structure, where each phosphorus atom is bonded to three other phosphorus atoms in a tetrahedron, and the bond angles are approximately 109.5°. This arrangement minimizes electron repulsion and maximizes stability. Thus, the \(\mathrm{P}_{4}\) molecule does not have a square planar structure, and statement e is false. In summary, statements b, c, and d are true, whereas statements a and e are false.

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Most popular questions from this chapter

In each of the following pairs of substances, one is stable and known, and the other is unstable. For each pair, choose the stable substance, and explain why the other is unstable. a. \(\mathrm{NF}_{5}\) or \(\mathrm{PF}_{5}\) b. \(\mathrm{AsF}_{5}\) or \(\mathrm{AsI}_{5}\) c. \(\mathrm{NF}_{3}\) or \(\mathrm{NBr}_{3}\)

Molten \(\mathrm{CaCl}_{2}\) is electrolyzed for \(8.00 \mathrm{~h}\) to produce \(\mathrm{Ca}(s)\) and \(\mathrm{Cl}_{2}(g)\) a. What current is needed to produce \(5.52 \mathrm{~kg}\) of calcium metal? b. If \(5.52 \mathrm{~kg}\) calcium metal is produced, what mass (in \(\mathrm{kg}\) ) of \(\mathrm{Cl}_{2}\) is produced?

Although He is the second most abundant element in the universe, it is very rare on the earth. Why?

Nitrous oxide \(\left(\mathrm{N}_{2} \mathrm{O}\right)\) can be produced by thermal decomposition of ammonium nitrate: $$ \mathrm{NH}_{4} \mathrm{NO}_{3}(s) \stackrel{\text { heat }}{\longrightarrow} \mathrm{N}_{2} \mathrm{O}(g)+2 \mathrm{H}_{2} \mathrm{O}(l) $$ What volume of \(\mathrm{N}_{2} \mathrm{O}(g)\) collected over water at a total pressure of \(94.0 \mathrm{kPa}\) and \(22^{\circ} \mathrm{C}\) can be produced from thermal decomposition of \(8.68 \mathrm{~g} \mathrm{NH}_{4} \mathrm{NO}_{3} ?\) The vapor pressure of water at \(22^{\circ} \mathrm{C}\) is 21 torr.

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