Hi! We already finished this lab for calorimetry, but I'm not sure how to complete this question. Thanks for the help!

Question

Briefly describe the three assumptions made in carrying out this experiment. Compare your calculated enthalpy of formation of (NH4)2SO4(s) to the actual enthalpy of formation value (-1180 kJ/mol). Based on this comparison, comment as to whether or not the three assumptions are valid and comment on any potential sources of error.

These are the assumptions from the lab
"In carrying out this experiment, we were required to assume that the calorimeter used was completely insulated and prevented heat from being lost or gained (for the surroundings). We also assumed that the solution’s density and heat capacity were the same as the heat capacity (4.184𝐽/ 𝑔∙°𝐶) and density of water (1.00𝑔/𝑚L). Furthermore, it was assumed by those carrying out the experiment that the reaction took place in an open-aired environment with constant pressure conditions where the reaction vessel is not completely secured."