3. Single Correct- points How many grams of KBr are required to make 850, mL of a 0.115 M KBr solution numerical value units 4. Single Correct- 10.0 points The first-order isomerization reaction: cyclopropane-propene, has a rate constant of 1.10 x 10-4 s-1 at 470°C and 5.70 x 10-4 s-1 at 500°C. What is the activation energy, Ea, for the reaction? numerical value units 5. Single Correct- 10.0 points What is the value for Kc for the following reaction: PbCl2(s) Pb2+(aq) + 2 Cl-(aq), = if PbCl2(s) = 1.50 grams, [Pb2+] = 1.6 x 10-2 M and [Cl-] = 3.2 x 10-2 M at equilibrium? (The molar mass of PbCl2(s) is 278 g/mol and its density is 5.85 g/cm³.) numerical value units