You would like to determine the reaction enthalpy for Zn(s) + 2HCl(aq) ? ZnCl2(a

Question

You would like to determine the reaction enthalpy for Zn(s) + 2HCl(aq) ? ZnCl2(aq) + H2(g) In part 1 of your experiment you mix 50.0 ml of 2.00 M HCl with 50.0 ml of 2.00 M NaOH. Temperature of the solution rises from 16.9 to 30.4 oC. You determine the density of the resulting solution to be 1.04 g/ml. In part 2 of your experiment you use 100.0 ml of 1.0 M HCL and 1.3078 g of Zn(s). Density of 1.0 M HCl is 1.015 g/ml and heat capacity of the ZnCl2 solution is 3.95 J g-1 K-1. In addition, you look up the heat capacity of water (4.18 J g-1 K-1) and 1.0 M NaCl (3.93 J g-1 K-1); the enthalpy of neutralization for NaOH and HCl is -57.32 kJ mol-1. a) determine calorimeter constant b) determine reaction enthalpy for the Zn / HCl reaction c) if ?fHo (ZnCl2 aq) is -482.2 kJ mol-1 and ?fHo (HCl aq) is -165.2 kJ mol-1, what is you percent error?

Explanation / Answer

formula: q=mST want: Delta H step 1: find T, using Tf-Ti step 2: assume mL of soln. is g step 3: use formula and solve for q step 4: g Zn to mol Zn step 5: to find Delta H, q/mol step 6: convert J to kJ step 7: ANS

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