Enthalpy

background [prelab assignment (25 points) due at the beginning of the lab]

This laboratory activity is based on investigation 12 in your AP chemistry lab manual; thus, it provides some relevant background for the following prelab questions and this laboratory activity.

1. based on the description in Procedure / part 2 & the remainder of the chapter in investigation 12 in the AP chemistry lab manual, determine the calorimeter's heat capacity (the lab manual uses the term, "calorimeter's constant", instead of heat capacity) based on the below hypothetical experimental data

mass of hot water = 100.0 g
mass of cold water = 100.0
initial T of cold water = 21.2 °C
initial T of hot water = 53.0 °C
final T of mixture = 36.8 °C

2. design / describe an experimental protocol to determine the heat of fusion of ice

3. Using Hess' law, what is the relationship between the below reactions ?

dissolve solid NaOH in HCl solution

dissolve solid NaOH in water

mix NaOH solution & HCl solution

4. sketch a data table for this lab containing entries for all required experimental measurements [i.e. review purpose & content of lab report]

5. download / save the *.swf file then use Ruffle to run simulation to analyze the simulated data to dissolve 2.0 g NH4NO3 in 100 g water to determine the ΔH (in kJ / mol) to dissolve solid ammonium nitrate in water.

purpose

experimentally, determine the heat of fusion of ice

experimentally, determine ΔH

dissolve solid NaOH in water,  i.e. NaOH(s) -> NaOH(aq) [or Na+(aq) + OH-(aq)]

dissolve solid NaOH in a HCl solution,  i.e. NaOH(s) + HCl(aq) -> H2O + NaCl(aq)

using the above information, determine the change in enthalpy to mix NaOH & HCl solutions,  i.e. NaOH(aq) + HCl(aq) -> products

compare experimental versus theoretical ΔH using statistics

determine the calorimeter's heat capacity

materials

NaOH, HCl, water, ice

coffee cup; thermometer

balance; hot plate

methods [delegate lab work]

heat of fusion of ice:  student design  [use an amount of water & ice, such that the final temperature is between 5 - 15 °C]

Δ H to dissolve solid NaOH in water: add ~2 g NaOH to 50 mL water

Δ H to dissolve solid NaOH in HCl solution: add ~2 g NaOH to 50 mL 2 .0 M HCl

determine the calormeter's heat capacity (student design), where the total volume of added water ~ 50 mL

data analysis

student design

 

Content of lab report [60 points]

data analysis 

data table(s) of your experimental measurements [5 points]

based on your group's data and ignore the calorimeter's heat capacity, determination of the experimental values of ΔH of the below reactions (express on a mole basis) [20 points]

experimental determination of the calorimeter's heat capacity [5 points]

include calorimeter's heat capacity in calculation of __ (10 points)

determination of the theoretical  value of the ΔH to dissolve solid NaOH in water (5 points)

statistical analysis (include interpretation of p-value) of class data; effect of including calorimeter's heat capacity in the determination of __ (10 points)

ΔHfusion

dissolve solid NaOH in water

conclusion: importance of including the calorimeter's heat capacity in your calculations; support your conclusion. (5 points)

resource

lab activity source (example):  site 1 

example calculation