Question

Mass of metal slug (measure once and use for both runs) 49.614 g 54.687 g Mass of water in calorimeter cup 80.113 g 80.087 g Initial temperature of water in the calorimeter 22.0 ºC 22.0ºC Initial temperature of the metal (assume 100.0 ºC) ____________ºC _____________ºC Equilibrium temperature of the metal + water 26.8 ºC 26.6ºC in the calorimeter ΔTwater ____________ºC ____________ºC ΔTmetal ____________ºC _____________ºC qwater * (S.H.C.water = 4.184 J/ g °C ) ____________J _____________J qmetal ** ____________J _____________J Calculated specific heat capacity of the metal ____________ J /g°C ____________ J /g°C B. Enthalpy of Reaction (Dissolution) CaCl2 NH4NO3 Mass of water in calorimeter cup 100.00 g 100.00g Mass of solid compound used 10.026 g 10.041g Mass of solution formed ____________g _____________g Initial temperature of water 22.0ºC 22.0ºC Max (if it rises) or min (if it falls) temperature of solution 38.2ºC 15.1ºC ΔTsoln (use initial temp. of water for initial temp. of soln.) ____________ºC _____________ºC qsoln (assume S.H.Cof soln. = S.H.C. of water) ____________J _____________J qreaction (amount of heat absorbed by the reaction)* ____________J _____________J “Heat of solution” ** ____________J/g _____________J/g ΔrH *** ____________kJ/mol_____________kJ/mol Is the dissolution reaction exothermic or endothermic? ____________ _____________ Enthalpy of Reaction (Neutralization) Initial temperature of HCl solution 22.0ºC Initial temperature of NaOH solution 23.2ºC Final temperature of neutralized mixture 29.4ºC ΔT (for the initial temperature, average the initial temperatures of the HCl and NaOH) ____________ºC qsoln (assume all the heat is absorbed by 104 g soln.) ____________J qrxn for the neutralization reaction ____________J Number of moles of H2O formed by the reaction ____________mol ΔHr (in kJ per mole of H2O formed by the reaction) ____________kJ/mol Is the neutralization reaction exothermic or endothermic? _____________

Answer 1

Mass of metal slug (measure once and use for both runs) 49.614 g, 54.687 g
Mass of water in calorimeter cup 80.113 g, 80.087 g

Initial temperature of water in the calorimeter 22.0 ºC, 22.0ºC
Initial temperature of the metal (assume 100.0 ºC)100ºC, 100ºC
Equilibrium temperature of the metal + water 26.8 ºC, 26.6ºC in the calorimeter
ΔTwater 4.8ºC, 4.6ºC
ΔTmetal -73.2ºC, -73.4ºC

qwater * (S.H.C.water = 4.184 J/ g °C ) = m*cP*DT
80.113* 4.184*4.8 = 1609 J
80.087* 4.184*4.6 = 1541.4 J
qwater * (S.H.C.water = 4.184 J/ g °C )1609J, 1541.4J
qmetal ** -1609J, -1541.4J

specific heat capacity of the metal, cp = qmetal/DTmetal
1609/73.2 = 22 J/g C
1541.4/73.4= 21 J/g C

Calculated specific heat capacity of the metal 22 J /g°C, 21 J /g°C

B. Enthalpy of Reaction (Dissolution) CaCl2 NH4NO3
Mass of water in calorimeter cup 100.00 g, 100.00g
Mass of solid compound used 10.026 g, 10.041g
Mass of solution formed 110.026g,110.041g
Initial temperature of water 22.0ºC, 22.0ºC
Max (if it rises) or min (if it falls) temperature of solution 38.2ºC, 15.1ºC

ΔTsoln (use initial temp. of water for initial temp. of soln.) 16.2ºC, -6.9ºC
qsoln (assume S.H.Cof soln. = S.H.C. of water = 4.184 J/ g °C ) = m*cP*DT
110.026* 4.184*16.2 = 7547.65 J
-110.041* 4.184*6.9 = -3176.8 J

qsoln (assume S.H.Cof soln. = S.H.C. of water) 7547.65J, -3176.8J
qreaction (amount of heat absorbed by the reaction)*-7547.65J, 3176.8J
“Heat of solution” ** = qreaction/mass of solid
-7547.65/10.026 = -752.8
3176.8/10.041 =    316.4
“Heat of solution” ** -752.8 J/g, 316.4 J/g

Molar mass:
CaCl2 = 111 g/mol
NH4NO3 = 80 g/mol

ΔrH = Heat of solution*MW
CaCl2: -752.8*111= -83561J = -83.56kJ/mol
NH4NO3 = 316.4*80 = 25312 J = 25.312 kJ/mol

ΔrH *** -83.56 kJ/mol, 25.312 kJ/mol
Is the dissolution reaction exothermic or endothermic? exothermic, endothermic

Enthalpy of Reaction (Neutralization)
Initial temperature of HCl solution 22.0ºC
Initial temperature of NaOH solution 23.2ºC
Final temperature of neutralized mixture 29.4ºC
ΔT (for the initial temperature, average the initial temperatures of the HCl and NaOH)
29.4-1/2*(22+23.2)=6.8C
ΔT (for the initial temperature, average the initial temperatures of the HCl and NaOH) 6.8 ºC
qsoln (assume all the heat is absorbed by 104 g soln.) 104*4.184*6.8= 2959 J

qsoln (assume all the heat is absorbed by 104 g soln.) 2959 J
qrxn for the neutralization reaction -2959J
Is the neutralization reaction exothermic or endothermic? exothermic