Question

I'm not sure if my calculations are correct:

Part A: Solving for Calorimeter Constant

TRIAL 1

Involving 50 mL of 1.83M HCl and 50 mL of 2.08M NaOH, trial 1 lasted for 9 minutes, temperature rose from 21.5 celsius to 34.3 celsius in 3.15 minutes and then fell to 32.3 celsius at the end of the 9 minutes

Solutions

Temperature change >>>> 12.80 celsius

Average temperature change >>>> 1.2 celsius / sec

Mass of solution, g >>>> 7.50g

Solution heat capacity, C_s, Joule/Kelvins >>>> 404.4 J/K

deltaH_rxn, Joule >>>> -5554 J

Calorimeter Constant, C_c, Joule/Kelvin >>>> -465.5 J/K

Part B: Calculation of Enthalpy of Neutralization

TRIAL 1

Involving 50 mL of 2.18M HNO3 and 50 mL of 2.16M NH3, trial 1 lasted for 9 minutes, temperature rose from 22.5 celsius to 35.8 celsius in 3.5 minutes and then fell to 33.7 by the end of the 9 minutes

Solutions

Temperature change >>>> 13.30 celsius

Average temperature change >>>> 1.24 celsius / sec

Mass of solution, g >>>> 102.9g

Solution heat capacity, C_s, Joule/Kelvins >>>> 401.31 J/K

deltaH_rxn, Joule >>>> -5726.1 J

Molar Enthalpy of neutralization >>>> -53.0 kJ

Part C: Enthalpy of Dissolution of Ammonium Salt

TRIAL 1

Involving 8.164g of NH4NO3 in 100 mL of H2O, trial lasted for 9 minutes, temperature fell from 23.2 celsius to 16.8 celsius in 4 minutes and then rose to 17.0 celsius by the end of the 9 minute trial.

Solutions

Temperature change >>>> 7.90 celsius

Average temperature change >>>> -.566 celsius / sec

Mass of solution, g >>>> 108g

Solution heat capacity, C_s, Joule/Kelvins >>>> 421 J/K

deltaH_rxn, Joule >>>> 3565J

Molar enthalpy of dissolution >>>> -32.3 kJ/mol

Answer 1

Part A: for Calorimeter Constant

A calorimeter constant (denoted C_cal) is a constant that quantifies the heat capacity of a calorimeter. It can be calculated by applying a known amount of heat to the calorimeter and measuring the calorimeter's corresponding change in temperature. In SI units, the calorimeter constant is then calculated by dividing the change in enthalpy (ΔH) in joules by the change in temperature (ΔT) in kelvins or degrees Celsius:

C_cal = ΔH/ΔT...................................(1)

ΔT =12.80 celsius = 285.95 K

Average temperature change = 1.2 celsius / sec

Mass of solution, g = 7.50g

Solution heat capacity, = 404.4 J/K

ΔH_rxn = -5554 J

Calorimeter Constant, C_cal = ΔH/ΔT

= -5554 /285.95

Calorimeter Constant, C_cal= - 19.42 J/K

Part B: Enthalpy of Neutralization

To determine the change in enthalpy in a neutralization reaction (ΔH_{neutralization}), a known amount of basic solution may be placed in a calorimeter, and the temperature of this solution alone recorded. Then, a known amount of acidic solution may be added and the change in temperature measured using a thermometer. The difference in temperature (ΔT, in units K or °C) may be calculated by subtracting the initial temperature from the final temperature. The enthalpy of neutralization ΔH_{neutralization} then calculated according to the following equation:

ΔH_{neutralisation} = C_cal x ΔT.....................................(2)

Regardless of the specific chemical process, with a known calorimeter constant and a known change in temperature the heat added to the system can be calculated by multiplying the calorimeter constant by that change in temperature.

T= 13.30 celsius= 286.45 K

Average temperature change= 1.24°/ sec

Mass of solution, = 102.9g

Solution heat capacity, = 401.31 J/K

H_rxn,= -5726.1 J

C_cal = ΔH/ΔT. = -5726.1 / 286.45 = -19.98 J/K

Enthalpy of neutralization = C_cal x ΔT

= -19.98 x 286.45

Enthalpy of neutralization = -5723.27 kJ

Part C: Enthalpy of Dissolution of Ammonium Salt

Temperature change T= 7.90 celsius = 281.05 K

Average temperature change= -.566 celsius / sec

Mass of solution, = 108g

Solution heat capacity, Cs= 421 J/K

H_rxn,= 3565J

Molar enthalpy of dissolution = C_cal x ΔT

C_cal = ΔH/ΔT = 3565J / 281.05 K = 12.68 J/K

Molar enthalpy of dissolution = C_cal x ΔT

= 12.68 x 281.05

Molar enthalpy of dissolution of Ammonium Salt = 3563.71 KJ/mol