In order for the reaction 2al(s) + 6hcl(aq)→2alcl3(aq) + 3h2(g) to occur, which of the following must be true? a. al must be above cl on the activity series. b. al must be above h on the activity series. c. heat must be supplied for the reaction. d. alcl3 must be a precipitate.

B. Al must be above H on the activity series i took the test

answer: enthalpy

explanation:

for a exothermic reaction, the energy is released i.e. the energy of the products is lower than the energy of the reactants.

= enthaply

= energy of products

= energy of reactants

as , thus comes out to be negative. negative value of enthalpy shows that the reaction is exothermic.