1. Calculate the density of gold using the following information: gold is found in a face centered cubic lattice (fcc) with lattice parameter a = 409 pm (a is the length of the cube edge); the molar mass of gold is 196.97 g/mol; and Avogadro's Number = 6.022×1023. Hint: sketch the structure.
2. Calculate the lattice energy for MgBr2 using the following information: S(Mg) = 148 kJ/mol; IE1(Mg) = 737 kJ/mol; IE2(Mg) = 1476 kJ/mol; V(Br2) (vaporization energy) = 31 kJ/mol; D(Br2) = 193 kJ/mol; EA(Br) = 325 kJ/mol; and ΔH°f = –524 kJ/mol.
3. Metal oxides can be semiconductors because lattice vacancies can exist. These vacancies originate if the metal can attain multiple oxidation states by a low energy oxidation or reduction. Based on this principle, predict whether WO3 is an n-type semiconductore, a p-type semiconductor, or neither. Explain your reasoning. A Latimer diagram for W is given below.
W3 (–0.029 V) → W2O5 (–0.031 V) → WO2 (–0.119 V) → W
4. The conjugate base of boric acid (H3BO3) is B(OH)4– in aqueous solution. Write the balanced Brønsted-Lowry reaction of boric acid with water.
5. Write the balanced reaction for the disproportionation of HMnO4– into MnO4– and Mn2+.