Thermochemical Equations assignment and quiz

How much energy is released when 0.40 mol C6H6(g) completely reacts with oxygen? 2C6H6(g) + 15O2(g) → 12CO2(g) + 6H2O(g) What is the enthalpy of reaction for the decomposition of NO2(g)? 2NO2(g) → N2(g) + 2O2(g) This reaction is...

-1,268 kJ -67.68 kJ exothermic

The enthalpies of formation of the compounds in the combustion of methane, CH4(g) + 2O2(g) → CO2(g) + 2H2O(g) are CH4 (g): TriHf = -74.6 kJ/mol; CO2 (g): TriHf = -393.5 kJ/mol; and H2 O(g): TriHf = -241.82 kJ/mol. How much heat is released by the combustion of 2 mol of methane? Use TriHrxn = sum of Tri H products - sum of Tri H reactants -80.3 kJ -802.5 kJ -1,605.1 kJ -6,420.3 kJ

-1,605.1 kJ

Manganese dioxide (MnO2(s), TriHf = -520.0 kJ) reacts with aluminum to form aluminum oxide (AI2O3(s), TriHf = -1699.8 kJ/mol) and manganese according to the equation below. 2MnO2(s) + 4Al(s) → 2Al2O3(g) + 3Mn(s) What is the enthalpy of the reaction? Use TriHrxn = sum of Tri H products - sum of Tri H reactants -1,839.6 kJ -1,179.8 kJ 1,179.8 kJ 1,839.6 kJ

-1,839.6 kJ

What is the TriHf for this reaction? 16CO2(g) + 18H2O(g) → 2C8H18(l) + 25O2(g)

10,148 kJ

What is the enthalpy of reaction for the decomposition of calcium carbonate? CaCO3(s) → CaO(s) + CO2(g) This reaction is...

656.3 J endothermic

Which graph represents an exothermic reaction?

A

Which statement is true for most chemical reactions? An energy change occurs during the breaking and forming of bonds. The internal energy of the system increases during a reaction. Energy is released during the formation of reactants. The enthalpy of the products is higher than the enthalpy of the reactants.

An energy change occurs during the breaking and forming of bonds.

The enthalpy of combustion for octane (C8H18(l)), a key component of gasoline, is -5,074 kJ/mol. This value is the TriHrxn for which of the following reactions? 2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(g) C8H18(l) + 12.5O2(g) → 8CO2(g) + 9H2O(g) 16CO2(g) + 18H2O(g) → 2C8H18(l) + 25O2(g) 8CO2(g) + 9H2O(g) → C8H18(l) + 12.5O2(g)

C8H18(l) + 12.5O2(g) → 8CO2(g) + 9H2O(g)

Which statement about TriHf is true? It is zero for any compound in its standard state. It is positive when the bonds of the product store more energy than those of the reactants. It is negative when a compound forms from elements in their standard states. It is zero for any element that is in the liquid state.

It is positive when the bonds of the product store more energy than those of the reactants.

Which of these statements are true? Select all that apply. The TriHrxn for the reaction C(s) + O2(g) → CO2(g) is the same as the Tri Hf for CO2(g). The Tri Hrxn for the reaction Na(s) + Cl2(g) → 2NaCl(s) is the same as the TriHf for NaCl(s). The TriHf for Br2(l) is 0 kJ/mol by definition. To determine the TriHf for H2O(g), just reverse the sign of the TriHrxn for the reaction 2H2O(l) → 2H2(g) + O2(g). The TriHf for N2(l) is 0 kJ/mol by definition. The TriHrxn for the reaction 1.5H2(g) + 0.5N2(g) → NH3(g) is the same as the TriHf for NH3(g).

The TriHrxn for the reaction C(s) + O2(g) → CO2(g) is the same as the Tri Hf for CO2(g). The TriHf for Br2(l) is 0 kJ/mol by definition. The TriHrxn for the reaction 1.5H2(g) + 0.5N2(g) → NH3(g) is the same as the TriHf for NH3(g).

Hydrogen reacts with chlorine to form hydrogen chloride (HCl (g), TriHf = -92.3 kJ/mol) according to the reaction below. H2(g) + Cl2(g) → 2HCl Which statement is correct? Use TriHrxn = sum of Tri H products - sum of Tri H reactants The enthalpy of the reaction is -184.6 kJ, and the reaction is exothermic. The enthalpy of the reaction is -184.6 kJ, and the reaction is endothermic. The enthalpy of the reaction is 184.6 kJ, and the reaction is endothermic. The enthalpy of the reaction is 184.6 kJ, and the reaction is exothermic.

The enthalpy of the reaction is -184.6 kJ, and the reaction is exothermic.

Which statement is true if the TriHrxn of a reaction is positive? The reaction is endothermic. The reaction is exothermic. There is more reactant than product. There is more product than reactant.

The reaction is endothermic.

The TriHrxn of formation of carbon dioxide is negative. Which statement is true? The reaction is endothermic. The reaction is exothermic. The amount of carbon dioxide is more than the amount of reactants. The amount of carbon dioxide is less than the amount of reactants.

The reaction is exothermic.

How is enthalpy used to predict whether a reaction is endothermic or exothermic? When the enthalpy of the reactants is higher than the enthalpy of the products, the reaction is endothermic. When the enthalpy of the products is higher than the enthalpy of the reactants, the reaction is exothermic. When the enthalpy change of the reaction is positive, the reaction is exothermic. When the enthalpy change of the reaction is positive, the reaction is endothermic.

When the enthalpy change of the reaction is positive, the reaction is endothermic.

Why do you think knowing enthalpy of reaction might be useful?

Which of these did you include in your answer? It allows scientists to predict the temperature change during a reaction. It allows scientists to determine how much of a reactant is necessary to produce a certain amount of energy. It allows scientists to predict whether a reaction might produce dangerous amounts of heat.

The enthalpy of formation for C6 H6 (I) is 49.0 kJ/mol. Consider the following reaction. 6C(s, graphite) + 3H2(g) → C6H6(l) Is the reaction endothermic or exothermic, and what is the enthalpy of reaction? Use TriHrxn = sum of Tri H products - sum of Tri H reactants exothermic; TriHrxn = 49.0 kJ exothermic; TriHrxn = -49.0 kJ endothermic; TriHrxn = 49.0 kJ endothermic; TriHrxn = -49.0 kJ

endothermic; TriHrxn = 49.0 kJ