Midterm 3 Bonding/Stoich

Which formulas represent one ionic compound and one molecular compound?

• N₂ and SO₂

• Cl₂ and H₂S

• BaCl₂ and N₂O₄

• NaOH and BaSO₄

Answer explanation

BaCl2 is an ionic compound formed from Ba2+ and Cl- ions, while N2O4 is a molecular compound made of covalently bonded N and O atoms. The other options do not contain one ionic and one molecular compound.

Which compound has both ionic and covalent bonding?

• CaCO₃

• CH₂Cl₂

• CH₃OH

• C₆H₁₂O₆

Answer explanation

CaCO3 contains both ionic and covalent bonds. The calcium (Ca) and carbonate (CO3) ions form ionic bonds, while the carbon and oxygen atoms within the carbonate ion are held together by covalent bonds.

Which element has atoms with the strongest attraction for electrons in a chemical bond?

• chlorine

• nitrogen

• fluorine

• oxygen

Answer explanation

Fluorine has the highest electronegativity of all elements, meaning it has the strongest attraction for electrons in a chemical bond. This makes it the most effective at pulling electrons towards itself compared to chlorine, nitrogen, and oxygen.

Which type of bond is found between atoms of solid cobalt?

• nonpolar covalent

• polar covalent

• metallic

• ionic

Answer explanation

Cobalt is a metal, and the atoms in solid cobalt are held together by metallic bonds. These bonds involve a 'sea' of delocalized electrons that allow for conductivity and malleability, characteristic of metallic substances.

Which Lewis electron-dot diagram represents a molecule having a nonpolar covalent bond?

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When lithium reacts with bromine to form the compound LiBr, each lithium atom

• gains one electron and becomes a negatively charged ion

• gains three electrons and becomes a negatively charged ion

• loses one electron and becomes a positively charged ion

• loses three electrons and becomes a positively charged ion

Answer explanation

When lithium reacts with bromine, it loses one electron to achieve a stable electron configuration, forming Li+. Thus, each lithium atom becomes a positively charged ion.

Which phrase describes a molecule of CH₄, in terms of molecular polarity and distribution of charge?

• polar with an asymmetrical distribution of charge

• polar with a symmetrical distribution of charge

• nonpolar with an asymmetrical distribution of charge

• nonpolar with a symmetrical distribution of charge

Answer explanation

CH4 (methane) is a tetrahedral molecule with symmetrical charge distribution due to identical C-H bonds. The equal sharing of electrons results in a nonpolar molecule, making the correct description 'nonpolar with a symmetrical distribution of charge'.

What is formed when two atoms of bromine bond together?

• a monatomic molecule

• a diatomic molecule

• a heterogeneous mixture

• a homogeneous mixture

Answer explanation

When two bromine atoms bond together, they form a diatomic molecule, which consists of two atoms of the same element. This is a characteristic of diatomic molecules, such as O2 or N2.

Which formula represents a molecule with the most polar bond?

• CO

• NO

• HI

• HCl

Answer explanation

HCl has the most polar bond due to the significant electronegativity difference between hydrogen and chlorine, leading to a strong dipole moment. In comparison, CO, NO, and HI have less polar bonds.

In a bond between an atom of carbon and an atom of fluorine, the fluorine atom has a

• weaker attraction for electrons

• stronger attraction for electrons

• smaller number of first-shell electrons

• larger number of first-shell electrons

Answer explanation

In a bond between carbon and fluorine, fluorine has a stronger attraction for electrons due to its higher electronegativity compared to carbon. This means fluorine pulls the shared electrons closer, making it more electronegative.