Question

Chemical cold packs used for sports injuries are made with solid ammonium nitrate (NH4NO3) and a plastic bag of water. When the bag of water is broken the ammonium nitrate dissolves.

NH4NO3(s) --> NH4+ (aq) + NO3- (aq)

As the solution forms, the water and bag get colder.

Which of the following is true for this process. ( Assume the reaction above is our system) Chose all that apply

Select one or more:

a. The process is endothermic.

b. Δ H for the reaction is positive

c. q for the water is positive.

d. The process is exothermic.

e. The solid ammonium nitrate has more enthalpy (H) than the ammonium and nitrate ions.

f. q for the water is negative.

g. The solid ammonium nitrate has less enthalpy (H) than the ammonium and nitrate ions.

h. q for the reaction is negative.

i. q for the reaction is positive.

Answer 1

NH4NO3(s) --> NH4+ (aq) + NO3- (aq)

As the solution forms, the water and bag get colder.

Select one or more:

a. The process is endothermic. True as the bag got colder, that is heat is absorbed.

b. Δ H for the reaction is positive. TRUE. For endothermic reactions by convention DH is taken positive.

c. q for the water is positive.TRUE Both water and NH4NO3 are part of system, so q(heat) is absorbed and positive.

d. The process is exothermic.False

e. The solid ammonium nitrate has more enthalpy (H) than the ammonium and nitrate ions. FALSE . Then DH = H of products - Hof reactants will be negative and DH is negative and rxn would be exothermic. But not the case .So FALSE

f. q for the water is negative. False

g. The solid ammonium nitrate has less enthalpy (H) than the ammonium and nitrate ions. True than DH is positive and endothermic reactions.

h. q for the reaction is negative. False

i. q for the reaction is positive. TRUe as it is endo thermic an d q = DH with same sign