forces. Both bromine and chlorine are nonpolar molecules and therefore have dispersion
forces. The dispersion forces are stronger for the bromine since it has many more electrons
than chlorine and these electrons are farther from the nucleus. Therefore, the electrons in
bromine are easier to polarize than chlorine and lead to stronger dispersion forces.
117. Part C
24 . C
Since q = mc∆T and q and m are held constant, c is inversely proportional to ∆T. Therefore, the
highest ∆T would be occur in the metal with the smallest heat capacity. Zinc has the smallest
heat capacity and therefore, the sample with largest temperature increase.
25 . A
The heat of reaction is the (sum of the heats of formation of the products) − (sum of the heats
of formation of the reactants).
Heat of reaction = heat of formation of N 2 O 4 − 2 (heat of formation of NO 2 )
(1 mol)(10 kJ/mol) − [(2 mol)(34 kJ/mol)] = −58 kJ.
26 . A
Both PbSO 4 and KNO 3 are products of the reaction. The PbSO 4 is insoluble and, therefore, the
precipitate. The KNO 3 is soluble in water.
27 . C
A strong electrolyte is a substance that dissociates or ionizes completely in water into its ions
to form an electrically conducting solution. CaCl 2 is the only ionic compound and it dissociates
completely. All the other compounds are molecular and don’t completely ionize when
dissolved.
28 . C
Molarity is moles of solute per liter of solution. To prepare 500 ml of 1.00 M solution, 0.5 moles
is needed. The molar mass of potassium chloride is 74.5 grams. So 37.3 grams of KCl is needed.
