Propane combusts according to the balanced equation C_3H_8(g)+5 ,O_2(g) ; ;3…

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

Propane combusts according to the balanced equation C3H8(g)+5 O2(g)  ⟶  3 CO2(g)+4 H2O(l)\mathrm{C_3H_8(g)+5\,O_2(g)\;\longrightarrow\;3\,CO_2(g)+4\,H_2O(l)} with an enthalpy change of ΔH=−2.220×103 kJ mol−1\Delta H=-2.220\times10^{3}\,\text{kJ\,mol}^{-1} for the combustion of one mole of propane. A portable heater must supply 3.56 MJ3.56\,\text{MJ} of thermal energy during an outdoor event. (a) Calculate the amount of propane, in moles, that must react to release the required thermal energy. (b) Convert the quantity obtained in part (a) to mass in grams. (c) State whether the combustion is exothermic or endothermic and justify your choice using the sign of ΔH\Delta H.

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