A student evaluates ammonium nitrate, \(\text{NH}_4\text{NO}_3\), for use in an instant cold pack by dissolving a known amount of the solid in water. The dissolution is endothermic. Initially, the water, solid, and room are at the same temperature. The student performs the experiment in a covered, thin-walled vessel without an insulating jacket and calculates the enthalpy of dissolution using

\[q_{\text{solution}}=m_{\text{solution}}c_{\text{solution}}(T_f-T_i)\]

and

\[\Delta H_{\text{soln}}=-\dfrac{q_{\text{solution}}}{n_{\text{NH}_4\text{NO}_3}}\]

Assume that heat exchange with the room is the only significant source of error. Compared with the accepted positive value of \(\Delta H_{\text{soln}}\), how will the calculated value be affected, and why?