During the experiment, scientists noted that several of the reaction beakers became hot to the touch. All of the following reactions could cause this result except endothermic and positive ∆H experiments.
Step-by-step explanation:
If the beakers are becoming hot during experimentation, then that means the energy is being released from the reactants during this experiment. As the energy is being released that enthalpy change will also be negative as the enthalpy change is calculated as the difference of enthalpy of reactants from products.
So in these cases, heat is released making the beakers hot. So for the exceptional case, the experiment should be endothermic in nature and positive enthalpy change should be there in the experiment. Such that the heat will not be released leading to no heating of beakers.