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Determination of enthalpy change
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Recommended: Determination of enthalpy change
The Enthalpy Change of Different Alcohols
My aim is to compare the enthalpy change of combustion of different
alcohols in relation to the structure of each molecule.
The enthalpy change of combustion of a fuel is a measure of the energy
transferred when one mole of the fuel burns completely. In a chemical
reaction, bonds must either be made or broken, this involves an
enthalpy change. The formation of bonds is exothermic, energy is lost
to the surrounding; on the other hand, breaking bonds is endothermic,
energy is taken in. I obtain the value for the enthalpy change of each
fuel by using the formula:
Energy transferred from the fuel=cm∆T
where c is the specific heating capacity of water (4.17 Jg-1K-1)
-m is the mass of water, in g
-∆T is the change of temperature of the water
Apparatus
Apparatus I will use
Size of the apparatus
Value /quantity
distill water
/
>3 litres, as much as possible*
thermometer
0-110C thermometer
1
measuring cylinder
100 cm3
1
electronic balance
correct to 2 decimal places
1
Bunsen burner
/
1
draught shielding
each approx. 20cm x 20cm
5
metal calorimeter
***
4
clamp
about 1 meter
6
spirit burner with wick
/
4
match/wooden stick
/
as many as possible
burner cap
/
4
tile
as big as possible
1
Propan-1-ol
/
half filled the spirit burner *
Butan-1-ol
/
half filled the spirit burner *
Butan-2-ol
/
half filled the spirit
burne *
Cyclohexanol
/
half filled the spirit burner *
***-I will find out in preliminary test
*-Half filled the spirit burner because alcohol should be away from
First, 100 mL of regular deionized water was measured using a 100 mL graduated cylinder. This water was then poured into the styrofoam cup that will be used to gather the hot water later. The water level was then marked using a pen on the inside of the cup. The water was then dumped out, and the cup was dried. Next, 100 mL of regular deionized water was measured using a 100 mL graduated cylinder, and the fish tank thermometer was placed in the water. Once the temperature was stabilizing in the graduated cylinder, the marked styrofoam cup was filled to the mark with hot water. Quickly, the temperature of the regular water was recorded immediately before it was poured into the styrofoam cup. The regular/hot water was mixed for a couple seconds, and the fish tank thermometer was then submerged into the water. After approximately 30 seconds, the temperature of the mixture leveled out, and was recorded. This was repeated three
Start with the hot water and first measure the temperature. Record it. 8. Then pour 40 ml into the beaker. You can measure how much water was used by looking at the meniscus.
Our procedure though was not without its mistakes. These mistakes are vital because they affect the data we conclude. Theoretically, according to the balanced chemical equation, for every mole of hydrated cobaltous chloride that is being heated, the decomposition ensures that the compound decomposes into one mole of cobalt(II) chloride and six moles of gaseous water vapor. Thus, in theory we should lose the mass equal to six moles of water vapor in each trial. Unfortunately, this is not the case because we don’t have perfect lab conditions and factors such as the time heated, utilization of the same crucible, and the inconsistency of magnitude of the flame from the Bunsen burner all contribute to differences in mass percent change for each
== = Hess’s law of heat summation states that the value of DH for a reaction is the same whether it occurs directly or as a series of steps. This principle was used to determine the change in enthalpy for a highly exothermic reaction, the combustion of magnesium metal. Enthalpy changes for the reactions of Mg in HCl (aq) and MgO (s) in HCl (aq) were determined experimentally, then added to that for the combustion of hydrogen gas to arrive at a value of –587 kJ/mol Mg.
An Investigation Into How the Thickness of Insulation Affects the Time a Drink Takes to Cool Down
This is expressed as Δ +ve (delta positive). If the total energy put in is less than the energy created, then the substance warms up (it is exothermic). This is expressed as Δ -ve (delta negative). I will investigate eight different alcohols using an alcohol or spirit burner, to measure the energy change during burning by measuring the change in temperature of some water held in a container.
Jade Lim is young Asian student with little previous exposure to alcohol. After consuming one and a half Bacardi Breezer’s (1.5 standard drinks) she begins to feel nauseas and has a pulsating headache. It is important to understand the mechanism of action of ethanol in order to determine the potential effects on the patient. This report will investigate the underlying molecular mechanisms of ethanol.
Variables --------- During the experiments, the water will be heated using different spirit burners containing different alcohols. I will be able to change different parts of the experiment. These are the. Volume of water heated:
one gram of water by 1ºC. I chose to use water because it is safe,
= 3 ´ E(C-H) + 1 ´ E(C-O) + 1 ´ E(O-H) + 1.5 ´ E(O=O)
water has risen to 60°c I will then put the lid on the spirit burner
NaOH(aq)Â Â Â Â Â Â Â Â +Â Â Â Â Â Â Â Â Â HCl(aq)Â Â Â Â Â Â Â Â Â Â Â Â Â Ã Â Â Â Â Â Â Â Â Â Â Â Â NaCl(aq) Â Â Â Â Â Â + Â Â Â H2O(l).
This software enables you to simulate experiments. This means that I am able to quickly carry out experiments to help in planning for my investigation. ---------------------------------------------------------------------- Alcohol Temperature Increase (oC) Mass of burner before exp. (g) Mass of burner after exp.
Do you know what alcohol does to a human body over time? Alcohol has many characteristics that affect people differently. The different kinds of alcohol will affect individuals differently because of other variables such as body physique, how full one’s stomach is and how quickly the alcohol is consumed. Alcohol is considered to be a drug. It is under the class of a depressant, which means it slows down the vital functions. After drinking too much, alcohol can slur speech, produce unsteady movements, disturb perception, and slow reaction time. It also reduces a person’s ability to think rationally and distorts his or her judgements. Blood alcohol concentration is used to determine the level of intoxication of an individual by the weight
One of the most important things in caliometry is the caliometer. This is a device used to measure the quantity of heat in a reaction. There are many different types of caliometers, some are used to measure the heat capacity of materials, and others measure the aspects the heat generates by new or untested reactions, heat of combustion and burn rates. One type of caliometer is reaction caliometers. These measure heat energy released or absorbed during a reaction that occurs inside the caliometer. Bomb caliometer are used to measure heat of combustion of a particular reaction. Differential scanning caliometers heat flow into a sample is usually measured differentially. A popular caliometer used in biochemistry is called the isothermal titration caliometer. In this caliometer the heat of the reaction is used to follow a titration experiment. It is used in biochemistry because it t facilitates determination of substrate binding to enzymes. Other caliometers that are sometimes used are x-ray micocaliometer, and high-energy particle caliometer. These two caliometers are not as often used, but can still be included in the different types. It is apparent that there are many different types of caliometers and some are used more commonly than others