Exam 6: Principles of Chemical Reactivity: Energy and Chemical Reactions

In thermodynamics,a(n)________ is defined as the object,or collection of objects,being studied.The surroundings include everything else.

At constant pressure and 25°C,what is Δ_rH° for the following reaction 2C₂H₆(g)+ 7O₂(g)→ 4CO₂(g)+ H₂O(l) If the complete consumption of 22.7 g of C₂H₆ liberates -1178 kJ of heat energy?

If 50.0 g of benzene (C₆H₆)absorbs 2.71 kJ of energy in the form of heat at 25.0 °C,what is the final temperature of benzene? The specific heat capacity of benzene is 1.72 J/g ⋅ K.

A 18.6-g piece of gold (s = 0.129 J/(g·°C)),initially at 285.4°C,is added to 147.2 g of a liquid,initially at 27.9°C,in an insulated container.The final temperature of the metal-liquid mixture at equilibrium is 28.9°C.What is the identity of the liquid? Neglect the heat capacity of the container.

Hydrazine,N₂H₄,is a liquid used as a rocket fuel.It reacts with oxygen to yield nitrogen gas and water. N₂H₄( )+ O₂(g)→ N₂(g)+ 2 H₂O( ) The reaction of 6.50 g N₂H₄ evolves 126.2 kJ of heat.Calculate the enthalpy change per mole of hydrazine combusted.