Chapter 9, Problem 8SAQ

Manganese reacts with hydrochloric acid to produce manganese (II) chloride and hydrogen gas.
$\text{Mn}\left(\text{s}\right)\text{+2HCl}\left(\text{aq}\right)\to {\text{MnCl}}_{\text{2}}\left(\text{aq}\right){\text{+H}}_{\text{2}}\left(\text{g}\right)$
When 0.625 g Mn is combined with enough hydrochloric acid to make 100.0 mL of solution in a coffee-cup calorimeter, all of the Mn reacts, raising the temperature of the solution from 23.5 °C to 28.8 °C. Find $\Delta {\text{H}}_{\text{rxn}}$ for the reaction as written. (Assume that the specific heat capacity of the solution is 4.18 J/g°C and that the density of the solution is 1.00 g/mL.)

• -195 kJ
• -1.22 kJ
• -3.54 kJ
• -2.21 kJ