Butane (C4 H10(g), Delta. Hf = â€"125. 6 kJ/mol) reacts with oxygen to produce carbon dioxide (CO2 , Delta. Hf = â€"393. 5 kJ/mol ) and water (H2 O, Delta. Hf = â€"241. 82 kJ/mol) according to the equation below. 2 upper C subscript 4 upper H subscript 10 (g) plus 13 upper o subscript 2 (g) right arrow 8 upper C upper O subscript 2 (g 0 plus 10 upper H subscript 2 upper O (g). What is the enthalpy of combustion (per mole) of C4H10 (g)? Use Delta H r x n equals the sum of delta H f of all the products minus the sum of delta H f of all the reactants. â€"2,657. 5 kJ/mol â€"5315. 0 kJ/mol â€"509. 7 kJ/mol â€"254. 8 kJ/mol.

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.

The characteristic of two different types of reactions are shown below. reaction a: electrons are gained by the atoms of an element. reaction b: protons are lost by the atom of and element. which statement is true about the atoms of the elements that participate in the two reactions? a: their identity changes in both reaction a and b. b: their identity changes in reaction a but not b. c: their identity changes in reaction b but not a. d: their identity remains the same.

An object displaces 652 ml of water. the volume of the object is: 0.652 cm³ 6.52 cm³ 65.2 cm³ 652 cm³