Use the equation and bond energies to answer the question. 2H₂O ⇒ 2H₂ + O2
H-O: 467 kJ/mol
H-H: 432 kJ/mol
O=O: 495 kJ mol

What is the total energy of the reaction? Is this an endothermic or exothermic reaction?

A. -509 kJ/mol, endothermic
B. 509 kJ/mol, endothermic
C. -509 kJ/mol, exothermic
D. 509 kJ/mol, exothermic

(Energy in Chemical Reaction Unit I test)

A3.37-mg sample of protein was chemically digested to convert its nitrogen into ammonia and then diluted to 100.0 ml. then 10.0 ml of this solution was placed in a 50-ml volumetric flask and treated with 5 ml of phenol solution plus 2 ml of sodium hypochlorite solution. the sample was diluted to 50.0 ml, and the absorbance at 625 nm was measured in a 1.00-cm cuvette and found to be 0.486. for reference, a standard solution was prepared from 10.0 mg of nh4cl (molar mass = 53.49 grams/mole) dissolved in 1.00 l of water. then 10.0 ml of this standard was placed in a 50-ml volumetric flask, treated in the same manner as the unknown, and the absorbance found to be 0.323. finally, a reagent blank was prepared using distilled water in place of unknown, it was treated in the same manner as the unknown, and the absorbance found to be 0.076. calculate the weight percent of nitrogen in the protein.

Calculate the number of kilojoules to warm 125 g of iron from 23.5°c to 78.0°c.

16. in a reaction that has reached equilibrium, a. the forward and reverse reactions are occurring at the same rate. b. the reactants and products are in equal concentrations. c. the forward reaction has gone further than the reverse reaction. d. there are equal numbers of atoms on both sides of the equation. e. a, b, and d are correct.