# Acetylene torches (C2H2) are commonly used in welding

CHY102 Chapter 6 ProblemsProblem 1Iron metal is obtained by reacting iron oxide with carbon monoxide according to thebalanced chemical equation:Fe2O3(s) 3 CO(g) 2 Fe(s) 3 CO2(g)Which species is being oxidized? Which species is the oxidizing agent? Using a table ofstandard enthalpies of formation calculate the enthalpy of this reaction (?rH°). Is thisreaction exothermic or endothermic? How much energy is evolved/absorbed (in kJ) when2.50 g of Fe2O3 is reacted with an excess amount of carbon monoxide?Problem 2Acetylene torches (C2H2) are commonly used in welding with the followingthermochemical equation:C2H2(g) 5/2 O2(g) H2O(g) 2 CO2(g)?rH° = -1255.5 kJ/molWhen 6.50 g of acetylene reacts with a stoichiometric amount of oxygen at atmosphericpressure the volume decreases by 2.80 L. Calculate the work done (in kJ; remember toinclude the sign (±)) and the change in internal energy of the system (in kJ; remember toinclude the sign (±)).Problem 3A chemist is studying a combustion reaction which involves a large increase in thenumber of moles of gaseous species. Suppose the chemist wants to obtain the maximumpossible heat from this chemical reaction. Should she carry out the reaction underconstant volume conditions or under constant pressure conditions?Problem 4A particular bomb calorimeter has a heat capacity of 5.86 kJ/°C. When 0.514 g of C12H10undergoes combustion in this bomb calorimeter the temperature rises from 25.8 °C to29.4 °C. Calculate the change in internal energy (?rU°) for the combustion of one mole ofC12H10.Problem 5

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