An athlete can apply an instant cold pack after an injury to help reduce swelling. An instant cold pack is a small bag containing two pouches, one filled with water and the other filled with ammonium nitrate (NH4NO3). The athlete activates the pack by squeezing the bag to break the pouches open, allowing the water and ammonium nitrate to mix. When this happens, the ammonium nitrate dissolves in the water, forming ammonium ions (NH4+) and nitrate ions (NO3−), and the pack becomes cold. Is this chemical exothermic or endothermic?

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2