In an exothermic reaction, heat is evolved, and the system loses heat to the surrounding. For such a system
A. qp will be negative
B. ΔrH will be negative
C. qp will be positive
D. ΔrH will be positive
Reason: In an exothermic reaction heat is released which is indicated by the negative sign of ΔrH.
And we know the relation that ΔH=qp, at constant pressure.
So, if ΔH is negative which means thatqpwill also be negative.
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The reaction of cyanamide, NH2CN (s), with dioxygen was carried out in a bomb calorimeter, and DU was found to be –742.7 kJ mol–1 at 298 K. Calculate enthalpy change for the reaction at 298 K.
NCERT - Chemistry Part-I