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Chapter 20: Problem 104

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鈥檚 crust. d. One of the atoms in Teflon is fluorine. e. The \(P_{4}\) molecule has a square planar structure.

Short Answer

Expert verified
Statements b, c, and d are true. Statement a is false because nitric acid is stronger than phosphoric acid, and statement e is false because the \(P_4\) molecule has a tetrahedral structure, not square planar.

Step by step solution

01

Statement a: Phosphoric acid vs Nitric acid strength

To compare the strengths of phosphoric acid (H3PO4) and nitric acid (HNO3), we need to compare their acid dissociation constants (Ka). The larger the Ka, the stronger the acid. HNO3 has a Ka value of approximately \(10^{鈭�1.4}\), while H3PO4 has a Ka value of approximately \(10^{鈭�2.1}\) for its first dissociation. Since the Ka value of HNO3 is larger than that of H3PO4, nitric acid is a stronger acid than phosphoric acid. So, statement a is false.
02

Statement b: Lowest boiling point of noble gases

To determine the noble gas with the lowest boiling point, we can look at their positions in the periodic table. Noble gases belong to group 18, and their boiling points generally decrease as we move up the group. Helium (He) is the element at the top of this group, and it has a boiling point of only 4.22 K, which is the lowest among all noble gases. Therefore, statement b is true.
03

Statement c: Sulfur as a free element in the Earth's crust

Sulfur (S) can be found as a native or "free" element in the Earth's crust, usually near volcanic areas or hot springs where it forms as a result of the reaction between hydrogen sulfide and oxygen. It can also be found combined with other elements in minerals such as pyrite (FeS2), galena (PbS), and gypsum (CaSO4路2H2O). So, statement c is true.
04

Statement d: Teflon and fluorine atoms

Teflon is a well-known brand name for a type of polytetrafluoroethylene (PTFE), a polymer that consists of carbon and fluorine atoms. The repeating unit of PTFE is \(-CF_2-\), meaning that each carbon atom is bonded to two fluorine atoms. Since Teflon is made up of carbon and fluorine atoms, statement d is true.
05

Statement e: Structure of the P4 molecule

The \(P_4\) molecule is composed of four phosphorus (P) atoms. Its structure is not square planar but rather, tetrahedral, where each P atom is bonded to three other P atoms, forming a regular tetrahedron. Therefore, statement e is false. In conclusion, statements b, c, and d are true, while statements a and e are false.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

noble gases
Noble gases are unique elements found in Group 18 of the periodic table. They are known for their lack of reactivity. This is due to their full valence electron shells, making them stable and unwilling to form chemical bonds. Noble gases include helium, neon, argon, krypton, xenon, and radon.
  • Helium: The lightest noble gas with the lowest boiling point of 4.22 K.
  • Neon: Known for its bright emission in neon signs.
  • Argon: Often used in welding and illuminating light bulbs.
These gases are used in various applications due to their non-reactive nature, such as providing an inert atmosphere for certain chemical reactions.
boiling point
The boiling point of a substance is the temperature at which it changes from a liquid to a gas. In noble gases, the boiling point is notably low compared to other elements. This is because they exist as individual atoms rather than molecules. Consequently, they have very weak dispersion forces.
  • As you move up the noble gases on the periodic table, the boiling points decrease.
  • Helium has the lowest boiling point, highlighting its extremely weak intermolecular forces.
Additionally, the boiling point can give insight into the energy required for a phase transition, a critical factor for applications in cryogenics.
sulfur in Earth's crust
Sulfur is an abundant element found in the Earth's crust. Though it is present in various forms, it can also be found as a free element, particularly near volcanic regions or hot springs.
  • Sulfur often appears as a bright yellow mineral, typically forming as a reaction product.
  • It is essential in forming sulfur-containing minerals like pyrite and galena.
Sulfur plays a vital role in industrial processes and biological systems, including the manufacture of fertilizers and the synthesis of amino acids.
Teflon structure
Teflon, commercially known as polytetrafluoroethylene (PTFE), is a polymer primarily composed of carbon and fluorine atoms. It is known for its high resistance to heat and chemical reactions.
  • Each carbon atom in Teflon is bonded to two fluorine atoms, forming the repeating unit \(-CF_2-\).
  • This structure provides Teflon with its non-stick properties, commonly used in cookware.
The strong bonds between carbon and fluorine make Teflon an incredibly durable material, useful in many industrial applications beyond cookware.
phosphoric acid
Phosphoric acid, with the chemical formula H3PO4, is a mineral acid that is less strong compared to other common acids like nitric acid. It has multiple hydrogen atoms that can dissociate, adding to its versatility in various reactions.
  • The first dissociation step gives it a Ka of about \(10^{-2.1}\), indicating moderate acid strength.
  • Used in cleaning products, food flavorings, and fertilizers.
Phosphoric acid is also notable for forming phosphate salts, which play crucial roles in biological systems, especially in cellular energy transfer.
nitric acid
Nitric acid, HNO3, is a highly corrosive and strong mineral acid with significant industrial applications. It is stronger than phosphoric acid, as evidenced by its higher Ka value.
  • The Ka value for nitric acid is around \(10^{-1.4}\), pointing to its greater ability to donate protons.
  • Commonly used in the production of fertilizers, explosives, and in chemical synthesis.
Despite its corrosive nature, nitric acid is essential for manufacturing processes and has a significant impact on agriculture and industry. Safe handling practices are crucial to avoid skin burns and environmental harm.
chemical bonding
Chemical bonds are forces that hold atoms together in a molecule or compound. Understanding these bonds is essential for explaining the properties and behaviors of materials.
  • Covalent bonds: Involve sharing electron pairs between atoms.
  • Ionic bonds: Result from the electrostatic attraction between oppositely charged ions.
Knowledge of chemical bonding provides insight into molecular stability, reactions, and physical properties. Chemical bonds not only define material strength but also influence molecular geometry.
molecular structure
The molecular structure refers to the 3D arrangement of atoms within a molecule, dictating how a molecule interacts with others.
  • Structure determines function, reactivity, and some physical properties.
  • Molecular geometry is vital in fields like pharmacology, where molecular interaction is critical.
Molecules like water have bent structures that result in their unique properties, such as high surface tension. Understanding molecular structure helps in identifying how substances combine and transform in a reaction.
P4 molecule
The P4 molecule, consisting of phosphorus atoms, illustrates a distinct molecular structure. Unlike a flat square planar arrangement, this molecule adopts a tetrahedral geometry.
  • Each P atom is bonded to three others, forming a stable tetrahedron.
  • This structure allows P4 to exist naturally in nature, including in minerals like phosphorus-rich deposits.
The understanding of P4's structure assists in predicting its chemical behavior, reactivity, and role in industrial applications. It showcases how different bonding configurations can lead to diverse molecular shapes and characteristics.

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Most popular questions from this chapter

The heaviest member of the alkaline earth metals is radium (Ra), a naturally radioactive element discovered by Pierre and Marie Curie in \(1898 .\) Radium was initially isolated from the uranium ore pitchblende, in which it is present as approximately 1.0 g per 7.0 metric tons of pitchblende. How many atoms of radium can be isolated from \(1.75 \times 10^{8} \mathrm{g}\) pitch- blende \((1 \text { metric ton }=1000 \mathrm{kg})\) ? One of the early uses of radium was as an additive to paint so that watch dials coated with this paint would glow in the dark. The longest-lived isotope of radium has a half-life of \(1.60 \times 10^{3}\) years. If an antique watch, manufactured in \(1925,\) contains 15.0 \(\mathrm{mg}\) radium, how many atoms of radium will remain in 2025\(?\)

Sodium tripolyphosphate \(\left(\mathrm{Na}_{5} \mathrm{P}_{3} \mathrm{O}_{10}\right)\) is used in many synthetic detergents. Its major effect is to soften the water by complexing \(\mathrm{Mg}^{2+}\) and \(\mathrm{Ca}^{2+}\) ions. It also increases the efficiency of surfactants, or wetting agents, that lower a liquid's surface tension. The pK value for the formation of \(\mathrm{MgP}_{3} \mathrm{O}_{10}^{3-}\) is \(-8.60 .\) The reaction is $$ \mathrm{Mg}^{2+}(a q)+\mathrm{P}_{3} \mathrm{O}_{10}^{5-}(a q) \rightleftharpoons \mathrm{MgP}_{3} \mathrm{O}_{10}^{3-}(a q) $$ Calculate the concentration of \(\mathrm{Mg}^{2+}\) in a solution that was originally \(50 . \mathrm{ppm} \mathrm{Mg}^{2+}(50 . \mathrm{mg} / \mathrm{L} \text { of solution) after } 40 . \mathrm{g} \text { of }\) \(\mathrm{Na}_{5} \mathrm{P}_{3} \mathrm{O}_{10}\) is added to 1.0 \(\mathrm{L}\) of the solution.

What structural features do the molecules \(\mathrm{P}_{4}, \mathrm{P}_{4} \mathrm{O}_{6},\) and \(\mathrm{P}_{4} \mathrm{O}_{10}\) have in common?

\(\mathrm{Al}_{2} \mathrm{O}_{3}\) is amphoteric. What does this mean?

Captain Kirk has set a trap for the Klingons who are threatening an innocent planet. He has sent small groups of fighter rockets to sites that are invisible to Klingon radar and put a decoy in the open. He calls this the 鈥渇ishhook鈥� strategy. Mr. Spock has sent a coded message to the chemists on the fighters to tell the ships what to do next. The outline of the message is Fill in the blanks of the message using the following clues. (1) Symbol of the halogen whose hydride has the second highest boiling point in the series of HX compounds that are hydrogen halides. (2) Symbol of the halogen that is the only hydrogen halide, HX, that is a weak acid in aqueous solution. (3) Symbol of the element whose existence on the sun was known before its existence on earth was discovered. (4) The Group 5A element in Table 20.13 that should have the most metallic character. (5) Symbol of the Group 6A element that, like selenium, is a semiconductor. (6) Symbol for the element known in rhombic and monoclinic forms. (7) Symbol for the element that exists as diatomic molecules in a yellow-green gas when not combined with another element. (8) Symbol for the most abundant element in and near the earth鈥檚 crust. (9) Symbol for the element that seems to give some protection against cancer when a diet rich in this element is consumed. (10) Symbol for the smallest noble gas that forms compounds with fluorine having the general formula \(\mathrm{AF}_{2}\) and \(\mathrm{AF}_{4}\) (reverse the symbol and split the letters as shown). (11) Symbol for the toxic element that, like phosphorus and antimony, forms tetrameric molecules when uncombined with other elements (split the letters of the symbol as shown). (12) Symbol for the element that occurs as an inert component of air but is a very prominent part of fertilizers and explosives.
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