Acid-Base Neutralization Calorimetry

Purpose

The purpose of the experiment is to observe the temperature changes in a reaction of acids and bases. This observation will lead to the deduction of the type of reaction for instance it can be endothermic or an exothermic reaction. Additionally, the purpose of the experiment is to conduct the measurement of the enthalpy of neutralization of a strong acid and a base during constant conditions.

Introduction

Calorimetry refers to the science used in recording the observed changes that occurs due to the chemical reaction of given variables. As a result, there is observed heat changes from the reactions under specified constrains. The measurements are usually performed using an experimental instrument known as calorimeter, hence the term calorimetry. Generally, calorimetry gathers data concerning heat flows through the measurement of the changes in the temperature range.

The lab experiment that was conducted majorly concentrated on the calorimetry of the neutralization of acids and bases.

In the concept of heat, the specific heat is use d to refer to the amount of heat per any given unit of mass that is required to increase the temperature levels by 1^oC.

Qrxn=-Qcal where Qrxn refers to an acronym that represents a heat reaction. On the other hand, qcal refers to the heat released during the process of calorimetry. Therefore, the equation is generally used to denote that the overall heat released exothermically is a resultant of the heat lost during the process of the reaction of an acid and a base.

In the experiment, four reactions were reacted. Three of the four reactions involved the acid base reactions whose energy release is exothermic. The final reaction involved dissolving a salt in water to determine the amount of heat released during the process. The four equations for the reactions are as below:

Acid + base → Salt + water + heat ( for a neutralization reaction). 

1.      Hcl_(aq) + NaOH_(aq) =  NaCl_(aq)+H₂O_(l)+ Heat Released

2.      CH₃CO₂H + NaOH_(aq) =  CH₂CO₂H + NaOH₂ + Heat released. This is a double replacement reaction.

3.      HNO3 + NaOH_(aq)  = NaNO3 + H20 + Heat released. This is another double replacement reaction.

The last equation is a salt – water dissolution reaction. The outcome can be two way.

4.      KNO₃ + H₂O = HNO₃ + KOH or

KNO₃ + H₂O _(aq) = KNO3 + K2O

S = a chemical in a solid state

l = a chemical in liquid state.

Aq = a chemical in an aquatic state especially used to denote water.

When a reaction occurs, the heat can be released to the environment such kind of a reaction is called an exothermic reaction . Examples of the exothermic reactions include the reactions in the first three equations above.  On the other hand, an endothermic reaction is a reaction whereby heat is drawn from the environment during the reaction process. The dissolution of salt in water as in the fourth and final equation above was an example of an endothermic reaction. This is because the temperature changes were positive, leading to a conclusion that there was heat energy produced as a result of the reaction.

Eventually, the experiment conducted sought to answer various questions on the outcomes of the four reactions conducted. This included the determination of whether the reactions were exothermic or endothermic in nature, the results of acid base reactions and the results of a salt and water reaction.

Experimental Introduction.

Four experiments were carried out. The first three experiments were an acid- base neutralization experiment. The last experiment involved dissolving a salt in water. All the experiments were done under constant environmental conditions, with the initial temperature at the start of the reactions and the final temperature readings being noted down. Additionally, the total volumes of the chemicals reacting were noted as well. In the last experiment involving salt and water, both mass and volume were recorded.  The requirements for the experiment included a thermometer for noting the temperature change, a calibrated beaker for measuring the volume and a calorimeter.

Equation	Acid	Base	Total Volume ±0.2MolL	Initial temperature (T1) ±0.2oc	Final temperature Reading (T2) ± 0.2oc	Temperature Change ±0.2oc	ÄHrxn = qrxn/n,	ÄHmol = ÄHrxn/ total volume
	HCL	NaOH	0.3	22	35.4	13.4	8.40kJ	28kJ/Mol
	HNo3	NaOH	0.3	21.2	34.9	13.7	8.59kJ	28.63kJ/Mol
	CH3CO2H	NaOH	0.3	21.8	34.7	12.9	8.09kJ	26.96kJ/Mol
Salt	--------	Water Volume (mL)	Salt Mass ±0.2g	Initial Temperature (T1 oC)	Final Temperature Reading (T2 oC)	Temperature change	ÄHrxn = qrxn/n,	ÄHmol
		0.248	25g	21.6	12	-9.6	7.02kJ	28.30

Calculation for the temperature of uncertainties (ÄT ) = ((0.2°C)² + (0.2°C)²)^-2= 2 ^-2*0.2°C = 0.28°C

Calculation for mass Uncertainities = ((0.2g)² + (0.2g)²)^-2= 2 ^-2*0.2g = 0.28g

Calculation for volume uncertainities = ((0.2moL)² + (0.2moL)²)^-2= 2 ^-2*0.2MoL = 0.28moL

The basic assumptions in this experiment include : the density of the solution is equal to the density of water which is 1.0 g/mL.