[BobFarmer001]

Suppose there is an insulated, constant volume vessel which contains some gaseous reactant.  The gaseous reactant undergoes an endothermic reaction.  What would the signs of heat (q), work (w) and D(U) be equal to assuming the system is everything inside the vessel?

My reasoning was that because the vessel is perfectly insulated, there can be no exchange of thermal energy between the contents of the vessel and the surroundings, so q would be 0.

Likewise, because the vessel is a constant volume container and we are solely interested in the work of expansion/contraction, the work would also be 0.

Lastly, because D(U) (delta U) is equivalent to the sum of q and w, delta U would also be equal to 0.

Is this reasoning correct?