Chapter 13 - Structure and Shape

47) Describe the shapes and compare the polarities of HF and HBr molecules. In each case, identify the end of the molecule that is more positive.

Both molecules are linear. HF is more polar than HBr. The H end of each is more positive.

45) Is the carbon tetrachloride molecule, CCl4, which contains four polar bonds (C-Cl electronegativity difference 0.5) polar or nonpolar? Explain.

CCl4 molecules are nonpolar because the polar bonds are symmetrically arranged, which makes the molecule itself nonpolar.

68b) True or False? Electron-pair geometry is the direct effect of molecular geometry.

False

68c) True or False? If the geometry of a molecule is linear, the molecule must have at least one double bond.

False

68f) True or False? A molecule is polar if it contains polar bonds.

False

68a) True or False? Molecular geometry around an atom may or may not be the same as electron-pair geometry around the atom.

True

68d) True or False? A molecule with a double bond cannot have a trigonal pyramidal geometry around the double-bonded atom.

True

68e) True or False? A CO2 molecule is linear, but an SO2 molecule is bent.

True

68g) True or False? A molecule with a central atom that has one lone pair of electrons is always polar.

True

68i) True or False? Carbon atoms normally form four bonds.

True

68j) True or False? Hydrogen atoms never form double bonds.

True

68h) True or False? A molecule with a central atom that has two lone pairs and two bonded pairs of electrons is always polar.

True if central atoms are limited to four electron pairs.

78) What are the shapes of the following: a) 1,2-dibromoethene, C2H2Br2 (the bromine atoms are on different carbon atoms) b) acetylene, C2H2

a) Trigonal planar with 120 degree angles around both carbon atoms b) Linear