Experiment 7

1.	Safety
2.	Objectives/Overview
3.	Procedures
4.	Observations
5.	Equipment
6.	View Techniques A. Calibration of Temperature Probe B. Determination of Heat Capacity C. Heats of Solutions D. Temperature Extrapolation from Graph
7.	Waste Disposal/Clean-up
8.	Calculations/Set-ups
9.	Conclusions
10.	Grading Scale
11.	Sample Report Forms
11.	Review Prelab Questions
12.	Review Postlab Questions

Experiment 7
Enthalpy of Solution

CALCULATIONS/SET-UPS

NOTE: If a heat (q) is positive it indicates heat is absorbed(heat gained), if a heat (q) is negative it indicates heat is released(heat lost). If DT is positive it indicate an increase in temperature and if DT is negative it indicates a decrease in temperature.

ALSO, for all calculations it is assumed that the density of all solutions is the same as the density of water (1.00 g/mL).

HEAT CAPACITY OF THE CALORIMETER

T_f = final temperature extrapolated from the graph
T₁ = initial water temperature in the calorimeter before mixing (taken from graph)
T₂ = corrected temperature of the warm water before it is added to the calorimeter (measured by the alcohol thermometer and multiplied by the correction factor.)

Correction factor for the alcohol thermometer	T_BW = temperature measured by alcohol thermometer in boiling water
	T_IW = temperature measured by alcohol thermometer in ice/water slurry
	Correction factor = (T_BW -T_IW)/100
Temperature increase (DT)	T_f - T₁
Temperature decrease (DT)	T_f - T₂
Heat gained by cool water (q_cool)	s_water = 4.184 J/g°C
	m_cool = mass of cool water
	DT = T_f - T₁ (temperature increase)
	q_cool = m_cools_waterDT
Heat lost by warm water (q_warm)	s_water = 4.184 J/g°C
	m_warm = mass of warm water
	DT = T_f - T₂ (temperature decrease)
	q_warm = m_warms_waterDT
Heat lost to the calorimeter (q_cal)	q_warm = - { q_cool + q_cal }
	q_cal = - { q_cool + q_warm }
Heat capacity of calorimeter (C_cal)	DT = T_f - T₁ (temperature increase)
	q_cal = C_calDT
	C_cal = q_cal/DT

MOLAR ENTHALPY OF SOLUTION
(SOLIDS DISSOLVING - CaCl₂ and NH₄NO₃)

T_i = initial temperature of water in calorimeter before adding solid (taken from graph)
T_f = final temperature extrapolated from graph
C_cal = heat capacity of your calorimeter (determined in previous calculation)

Temperature increase (or decrease) (DT)	DT = T_f - T_i
Heat gained (or lost) by solution (q_soln)	q_soln = m_waters_waterDT
Heat gained (or lost) by calorimeter (q_cal)	q_cal = C_calDT
Heat evolved (or absorbed) by reaction (solid dissolving) (q_rxn)	q_rxn = - {q_soln + q_cal + q_solid}
	But, since q_solid is small enough to be ignored
	q_rxn = - {q_soln + q_cal}

Moles of solid (n)	n = (grams of solid)/(molar mass of solid)



Molar Enthalpy of Solution (DH)	DH = q_rxn / n