The as a result of formation of only one

The purpose of this experiment was to determine
the heat of neutralization for the reaction of sodium hydroxide (NaOH) and
hydrochloric acid (HCl). Heat of neutralization (Hn) refers to the
change in enthalpy that happens when one equivalent amount of an acid and a
base neutralize to form a salt and eventually water. It is an outstanding case
of enthalpy of reaction. This can also be defined as the energy that is
released as a result of formation of only one mole of water. The reactions that
take place in chemical sciences results to breaking and eventually breaking of
bonds. The reaction is accompanied by certain heat effects.  The formation
of chemical bonds tends to release as in the form of heat thus referred to as
exothermic reaction. On the other hand, endothermic reaction is one that is
associated with absorption of heat from the surrounding.

            Heat
of neutralization comes under the concept of calorimetry. Calorimetry is a detailed study of heat flow and
measurements. It is a scientific term
that deals with the changes in energy of the experiment by indicating the
changes in heat in the surrounding. Therefore, it can be defined to fully
determine the heat that is absorbed or eventually released in a chemical
reaction.   Scientists and chemists who study the heat
of reactions, measure the changes that take place in the environment that surrounds
the chemical reaction.  They do this through a device called a calorimeter.
A calorimeter is a device that splits the outer environment such that any loss/gain
of energy in the products would result in a change in temperature only inside
the calorimeter A calorimeter is made of
two vessels that is, the inner and the outer vessel. It usually just contains a thermometer which is attached to a
container and a stirrer which was used
to stir the solution. In this experiment, a Styrofoam cup
along with a thermometer were used as a calorimeter as such a cup has
well-insulated walls that would help in prevention of heat loss. So, basically the Styrofoam that is in between the space between the two
vessels acts as the insulator, thus minimizing the amount of heat lost to the
surrounding. Also, in general, a calorimeter makes sure that there is equal
distribution of heat.

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            The
reaction of NaOH and HCl resulted to a neutralization reaction which further
resulted in production of water and a base that is called NaCl. When the
solution was continuously stirred, a sudden spike in the temperature along with
the cup getting warm was felt. When checked with the thermometer, there had
been an evident increase in the temperature, thus, proving that the reaction is
exothermic in nature. When a powerful acid reacts with the same concentration
of base, the enthalpy change tends to be quite unique. The reaction of an acid
and base results in production of a salt and water, thus termed as
neutralization reaction. The bonds that are contained into the two solutions must
fully dissociate forming water, as it evident in the equations below.
 Besides that, there is a lot of breaking of bonds as the heat is absorbed
by the solution. The reaction that takes place is:

Acid  +  Base   ?  Alkali  +  Water

 

  

 

If carefully considered, the above reaction it
quite clear that the bonds are formed in order to dissociate the reaction.

           

If the expected value for the enthalpy change in
this particular reaction is -55.8 kJ/mol, the results will be actually based on the fact that there is a loss
of heat, as the reaction continues. There would be errors within the experiment
and a 100 % accuracy level cannot be guaranteed.

Heat
of neutralization=  

where: Q (amount heat transferred) = volume x density x heat capacity x ?t

                                                        
= (50+51) x 1.04 g/ml x 3.89 J g-1deg-1 x 9.98

                                                        
= 4077.88

no. of moles reacting = 0.10 moles (calculations
on data sheet)

Therefore, Heat
of neutralization = (4077.88/1000) / 0.10

                                                     
= 47.65

Therefore,
the enthalpy of neutralization will be -47.65 kJ/mol

So, the percentage error= (expected value – calculated
value) / expected value x 100

                                      = (55.8-47.65)/55.8 x 100

                                      = 14.6%

Based
on these results, the calculated value of heat of neutralization is -47.65
which when compared to the actual value (-55.8), is much lower. Also, the
margin of error for this experiment was 14.6% which is acceptable as it is not
a very large percentage. This reflects that the results have been quite
accurate. However, there could, perhaps, be a lot of reasons for this
variation. One reason cold be the type of calculator that was used. In this
experiment, a glass thermometer was used, and it was pretty hard to estimate
the temperature readings precisely. Also, because of that, the temperature
readings were rounded off to the nearest 10th degree. If, a digital
thermometer was used, readings would have been much more accurate, and the
readings could have been rounded to nearest 100th degree. Also,
another reason that could be stated is the lack of a polystyrene
lid/top. If, a polystyrene top would have been there, there would have been
more insulation and the heat loss would be quite less, which could have resulted
in more accuracy. In addition to that, a low neutralization value could be
because not all drops of base was transferred to the acid while mixing.

         If, instead of a
polystyrene cup, a glass cup was used, the value of heat of
neutralization would have astonishingly dropped. This is because the heat that will be transferred will be more
from hot to cold, that is, a significant loss of energy to the surrounding from the internal environment.
In the actual sense, experimentally the temperatures that will be recorded will
be low calculated enthalpy change. Similarly, if granulated cylinders,
after measuring the acid and before adding the base, weren’t rinsed or dried
properly, it would result in a lower value of heat of neutralization.  This is
simply because the base and the acid would have reacted before the process of mixing
acid and base which would result in consuming molecules which might have been
useful in providing energy. On the
other hand, placing a polystyrene top would have helped a lot. The results
would have been much more accurate as it would contain the additional
heat that would be lost to the environment by being exposed to surroundings.

         HBr
can only dissociate to form H+ ions as well as Br- ions. So,
it is only a question of which one is a positive charge and which is negative.
HNO3 also dissociates to form H+ ions. Both NaOH and
eventually KOH have got Hydroxide ions that make them alkalis. This
means that both NaOH and KOH disassociate completely and they both contribute
to OH to create a water molecule for the product. The energy and heat of
neutralizations of both the reactions would be the same as both the base and
the acids in the reaction fully disassociate and make water molecules.

KOH and Nitric acid will complete dissociate to:

 

 

1.     
HBr(aq)
+ NaOH(aq) —> H2O(l) + NaBr(aq)

Net ionic: H+(aq)
+ OH-(aq) —> H2O(l)

2.     
HNO3(aq)
+ KOH(aq) —> H2O(l) + KNO3(aq)

Net Ionic: H+(aq)
+ OH-(aq) —> H2O(l)

x

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