Description
for the deadline I only need the pre-lab.
after finishing the lab and taking data I will post the data for calculations and post lab.
Enthalpy determinations by calorimetry
-To study the interrelationship between heat, heat capacity, and temperature changes.
- To monitor temperature changes in the surroundings during physical and chemical reactions and correlate those changes to the endo- or exothermicity of the reacting system.
- To determine the heat capacity of a calorimeter.
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Explanation & Answer
Wow buddy it was a very hectic but enjoyable asignment please review it and notify me of any edits. Thank you and goodbye
Running head: CHEMISTRY PRELAB
Chemistry Pre Lab
Student Name
Institution Affiliation
Instructor’s Name
Date
1
CHEM LAB ENTHALPY
DETERMINATION THE ENTHALPY (OR HEAT) OF A REACTION BY USE
OF A CALORIMETER
1. PURPOSE
To apply the concepts of specific heat and temperature change in the experimental
determination of the heat of neutralization of strong acid by strong base and molar
enthalpy of solution of a soluble salt, and to compare the experimental value to the
accepted value for the enthalpy of solution for each salt.
2. INTRODUCTION
Chemical reactions usually accompany the formation and absorption of energy in
the form of heat. The branch of chemical science dealing with the study of heat
and energy changes is known as thermodynamics. The heat changes within a
specific system can be studied using the device calorimeter.
Calorimeter is derived from the Latin term “calor” which means heat, and the
Greek term “metry” means to measure, the heat in the system. The recent
advances in the calorimeter and electronics help the user to maintain the samples
under proper conditions that can be easily analyzed.
The heat change in chemical reactions in quantitatively is expressed as Enthalpy
(or heat) of reaction, ∆H, at constant pressure.
∆H values are negative for exothermic reactions
∆H values are positive for endothermic reactions
The quantitative of heat of reaction in the calorimeter is calculated:
Q = m.C (tf - ti) (1)
Chemistry Prelab
3
m: The mass of the sample which is heated up or cooled
C: Private thermal capacity (J/g.0C)
tf: The final temperature
ti: The initial temperature
Enthalpy ∆H of reaction is calculated:
H=
-Q
=
nreactant
-Q
(J/mol)
nsolution
3. MATERIALS AND INTRUMENTS
a)
MATERIALS
NaOH 1M
KOH 1M
HCl 1M
HNO3 1M
NaOH (solid or crystal)
NH4Cl (crystal)
NH4NO3 (solid or crystal)
b)
INSTRUMENTS
The Calorimeter tube
Beaker 10 ml
Glass funnel
Glass stirring rod
Graduated cylinder
Thermometer
(2)
4. PROCEDURE
4.1. Determination the Enthalpy of solution of NaOH (∆HsNaOH)
1. Put the distilled water (100 ml) in the Calorimeter tube (Figure), put on the lid,
gently shake and wait temperature is stable, we read ti value.
2. Put some NaOH (solid) on the dried bowl and scale to obtain mt (g).
3. Spill NaOH in the Calorimeter tube, gently shake until NaOH is soluted
completely, and oversee simultaneously the alteration on the thermo barometer.
4. When temperature is unchangeable, we read tf value
5. Scale the bowl again without NaOH (mb).
❖ The mass of NaOH was soluted: m1 = mt – mb
❖ The mass of solution in the reaction tube: m = m1 + mH2O
4.2. Determination ∆Hs of NH4Cl
After washing the Calorimeter tube, do the same work with NH4Cl.
4.3. Determination the Enthalpy of Neutralization of Acid- Base reaction
The reaction of a strong acid with a strong base is an exothermic reaction:
NaOH + HCl → NaCl + H2O
1. Put HCl 1M solution (50 ml) in the Calorimeter tube, put on the lid,
gently shake, wait about 4-5 minutes temperature is unchangeable and
read t1 value.
2. Put NaOH 1M solution (50 ml), read t2 value.
ti = 1/2 (t1 + t2)
ti: The initial temperature.
Chemistry Prelab
3
The reaction NaOH + HCl → NaCl + H2O is happening in the Calorimeter, we
observe the alteration of temperature in the thermo barometer, and this is the
final temperature of reaction (tf)
Calculation...