Question

A system which does work on the surroundings with no heat change (i.e., q = 0) has: Ow=AU Ow=-AU w>0, AU < 0 O w<0, AU > 0 Ο w > Δυ Question 2 4 pts For the reaction: 2A + B2 -> 2AB AH = +50.0 kJ. The reaction is endothermic The bond energy for each A-B bond is 50.0 kJ The molecule AB contains less energy than A or B2 Heat is released to the surroundings

Answer 1

Q.1) As , given that , no heat change , i.e.( q = 0 )

Therefore , from first law of thermodynamics ,

W = - ∆U .

Also , we know that ,

For a thermodynamic process without transfer of matter, the first law is often formulated ,

Δ U = Q − W

where ΔU denotes the change in the internal energy of a closed system, Q denotes the quantity of energy supplied to the system as heat, and W denotes the amount of thermodynamic work done by the system on its surroundings.

Q.2 ) as given , ∆H for the reaction is positive , therefore ,

The reaction is endothermic.

Also , When enthalpy is positive and delta H is greater than zero, this means that a system absorbed heat. This is called an endothermic reaction. When enthalpy is negative and delta H is less than zero, this means that a system released heat. This is called an exothermic reaction.