Enthalpy and Phase Changes Answers

Which statement about Hf is true?

Hydrogen ( H2 ) reacts with bromine ( Br2 ) to produce hydrogen bromide (HBr) gas as shown in the equation below.Standard Enthalpies of FormationSubstanceDHf (kJ/mol)Br2 (l)0.0Br2 (g)30.907HBr (g)–36.4HCl (g)–92.307HI (g)26.48H2 (g)0.0I2 (g)62.438Based on the equation and the information in the table, what is the enthalpy of the reaction?

Consider the reaction.Standard Enthalpies of FormationSubstanceDHf (kJ/mol)C2 H2 (g)226.73CaCO3 (s)–1206.92CaO (s)–635.09CO (g)–110.525CO2 (g)–393.509H 2 O (I)–285.8H 2 O (g)–241.818C (s), diamond1.895C (s), graphite0.0Based on the equation and the information in the table, what is the enthalpy of the reaction? Use .

The Hrxn of formation of carbon dioxide is negative. Which statement is true?

Sulfur reacts with oxygen to form sulfur dioxide (SO2(g), Hf = –296.8 kJ/mol) according to the equation below.What is the enthalpy change for the reaction? Use .

The enthalpies of formation of the compounds in the combustion of methane, ,are CH4 (g): Hf = –74.6 kJ/mol; CO2 (g): Hf = –393.5 kJ/mol; and H2 O(g): Hf = –241.82 kJ/mol.How much heat is released by the combustion of 2 mol of methane? Use .

Ammonia (NH3 (g), Hf = –45.9 kJ/mol ) reacts with oxygen to produce nitrogen and water (H2 O(g), Hf = –241.8 kJ/mol) according to the equation below.What is the enthalpy of the reaction? Use .

Manganese dioxide (MnO2(s), Hf = –520.0 kJ) reacts with aluminum to form aluminum oxide (AI2O3(s), Hf = –1699.8 kJ/mol) and manganese according to the equation below.What is the enthalpy of the reaction? Use .

The enthalpy of formation for C6 H6 (I) is 49.0 kJ/mol. Consider the following reaction.Is the reaction endothermic or exothermic, and what is the enthalpy of reaction? Use .

How is enthalpy used to predict whether a reaction is endothermic or exothermic?