Question

What will be the experimental enthalpy of reaction when 0.5000g of zinc reacts with 20.00mL of 1.500M HCl, changing the temperatrure of the solution (surroundings) in the calorimeter by +13.5C? Hint: write the balanced equation, and then calcualte how many moles are really reacting by determing of the limiting reactant. Assume density of solution is 1.000g/mL.

Answer 1

    Zn + 2HCl ---------> ZnCl2 + H2

no of moles of Zn = W/G.A.Wt

                               = 0.5/65.4   = 0.0076moles

no of moles of HCl   = molarity * volume in L

                                = 1.5*0.02 = 0.03 moles

2 moles of HCl react with 1 mole of Zn

0.03 moles of HCl react with = 1*0.03/2 = 0.015 moles of Zn

Zn is limiting reactant