Chemistry Quiz: Molecular Geometry

Explanation
The shape of a molecule plays an important role in its reactivity because it determines how the molecule can interact with other molecules. The shape affects the arrangement of atoms and the distribution of electron density, which in turn affects the molecule's ability to form and break chemical bonds. Different shapes can lead to different levels of stability and reactivity, as well as influence the types of reactions that a molecule can undergo. Therefore, the shape of a molecule is a crucial factor in determining its reactivity.

Explanation
NH3 is the correct answer because it is the only molecule in the given options that has 3 lone pairs bonded. In NH3, the central nitrogen atom is bonded to three hydrogen atoms, leaving one lone pair of electrons. This makes NH3 a trigonal pyramidal molecule with 3 lone pairs bonded. NaCl is an ionic compound and does not have any lone pairs. H2O has 2 lone pairs bonded, and BaCl2 has no lone pairs bonded.

Explanation
Not all molecules have three atoms with the same reactivity. The reactivity of atoms in a molecule depends on various factors such as their electronic configuration, bonding, and the presence of functional groups. Different atoms within a molecule can have different reactivities based on these factors. Therefore, the statement that every molecule with three atoms has the same reactivity is incorrect.

Explanation
BCl3 will have bond angles of 120. This is because BCl3 has a trigonal planar molecular geometry, where the central boron atom is surrounded by three chlorine atoms. The three chlorine atoms are arranged symmetrically around the boron atom, creating a bond angle of 120 degrees between them.

Explanation
The correct answer is "tetrahedral, 109.5". In H2O, the electron domain geometry is tetrahedral because there are four electron domains around the central oxygen atom. The angle is 109.5 degrees because the two bonding pairs and two lone pairs of electrons repel each other, causing the molecule to adopt a tetrahedral shape with a bond angle of 109.5 degrees.

Explanation
The electron domain geometry of CBr4, PH3, and CCl2Br2 is tetrahedral. This means that the central atom in each of these molecules is surrounded by four electron domains, resulting in a tetrahedral arrangement. However, XeF4 does not have a tetrahedral electron domain geometry. XeF4 has a square planar electron domain geometry, where the central xenon atom is surrounded by four electron domains arranged in a flat square shape. Therefore, the correct answer is all of the above except XeF4.

Explanation
The correct answer is "bent". This is because the NO2^-1 molecule has a central nitrogen atom bonded to two oxygen atoms. The electron arrangement around the nitrogen atom is trigonal planar, but due to the lone pair of electrons on the nitrogen atom, the molecule adopts a bent shape. This lone pair causes electron-electron repulsion, pushing the oxygen atoms closer together and resulting in a bent molecular geometry.

Explanation
NO2 is polar because it has a bent molecular geometry and a lone pair of electrons on the central nitrogen atom. This lone pair creates an imbalance in the distribution of electrons, resulting in a polar molecule.

Explanation
Molecular geometry refers to the arrangement of only the atoms in a molecule. It describes the spatial arrangement of the atoms in a molecule, including the bond lengths and bond angles. Electron domain geometry, on the other hand, refers to the arrangement of both the atoms and lone pairs of electrons around a central atom. Therefore, the correct answer is molecular geometry.

Explanation
CH3Cl is a polar molecule because it has a dipole moment. The chlorine atom is more electronegative than the carbon and hydrogen atoms, causing the electron density to be shifted towards the chlorine atom. This creates a partial negative charge on the chlorine atom and partial positive charges on the carbon and hydrogen atoms. As a result, CH3Cl has an uneven distribution of charge and is considered polar. BF3 and CCl4 are nonpolar molecules because they have symmetrical structures and no dipole moment.

Explanation
The molecule O=C=O, also known as carbon dioxide, is polar. This is because the oxygen atoms on either side of the carbon atom have a higher electronegativity than carbon, causing an unequal sharing of electrons. As a result, the oxygen atoms pull the electrons towards themselves, creating partial negative charges on the oxygen atoms and a partial positive charge on the carbon atom. This separation of charges makes O=C=O a polar molecule.