To determine enthalpy change Essay Example for Free

To determine enthalpy change Essay Chemistry Lab report 1) Experiment No: 8A 2) Objective: To determine the heat of formation of calcium carbonate. 3) Date: 26th Nov, 2010 4) Theory: The experiment consists of 2 parts: a) In the 1st part, an accurately weighed known mass of calcium is added to a given dilute hydrochloric acid. During the addition, the following occurs: Ca(s) + 2H+(aq) Ca2+(aq) + H2(g) With the help of the data of heat change of the solution mixture, the average heat evolved by one mole of calcium during the reaction can be calculated. b) In the 2nd part, an accurately weighed known mass of calcium carbonate is added to a given dilute hydrochloric acid. During the addition, the following occurs: CaCO3(s) + 2H+(aq) Ca2+(aq) + CO2(g) + H2O(l) With the help of the data of heat change of the solution mixture, the average heat evolved by one mole of calcium carbonate during the reaction can be calculated. After that, by using a suitable energy-cycle diagram, and applying Hesss law, the heat formation of formation of calcium carbonate can be calculated. 5) Procedure: Please refer to the lab. manual 6) Data: 1st Part: Reaction of calcium with dil. Hydrochloric acid Experiment No: 1 2 Mass of Ca used / g 0. 53 0. 51 Volume of hydrochloric acid used: 100cm3 2nd Part: Reaction of calcium carbonate with dil. Hydrochloric acid Experiment No: 1 2 Mass of CaCO3 used / g 2. 13 2. 05 Molar mass of calcium carbonate = 100 g/mol Volume of hydrochloric acid used = 100 cm3 7) Calculation: Note: No temperature drop can be observed after the max temperature is attained for 4 readings. Note: No temperature drop can be observed after the max temperature is attained for 4 readings. Extrapolation procedure cannot be done. Therefore, the temperature change of 1st part exp. = 28-25 = +3oC the temperature change of 2nd part exp = Enthalpy change in 2nd parts reaction Hf [H2O(l)] = -242000 J mol-1 Hf [CO2(g)]= -393500 J mol-1 source: physical chemisty I of Fillans By Hesss law: Hf[CaCO3(s)] = H1 + Hf [H2O(l)] + Hf [CO2(g)] H2 = -688. 79 kJ mol-1 8) Discussion 1. Why is the exact concentration of hydrochloric acid unimportant? The exact concentration of the hydrochloric acid was unimportant as it was present in excess, that was, to provide enough H+(aq) to react with calcium. At the same time, the exact concentration of hydrochloric acid would affect the calculation afterwards. 2. State the law which you use for calculating the heat of formation of calcium carbonate. On which thermodynamic principle does it depends? The law used was the Hesss law. It depends on the standard enthalpy change of a reaction is independent of the route by which the chemical reaction takes place, which only depends on the difference between the standard enthalpies of reactants and products, i. e. conservation of energy. 3. Why is this law useful? This principle is useful as the standard enthalpy change of some reaction might not be able to find directly, and thus Hesss law can be used and the standard the enthalpy change of the reaction can be calculated indirectly by this method. 4. Discuss the possible sources of errors. State how to minimize the possible errors. A. The solid labeled calcium is suspected to be calcium oxide, which show white color but not grey shinny color. B. Heat produced the reaction might heat up the air inside the beaker, which cannot be avoided. C. Error in reading thermometer D. Error in weighing.

Comparing Felicite of Flauberts A Simple Heart and Nelly Dean of Brontes Wuthering Heights :: comparison compare contrast essays

Comparing Felicite of Flaubert's A Simple Heart and Nelly Dean of Bronte's Wuthering Heights Nelly Dean and Felicite are both characters that are in stark contrast to the characters that surround them. They are both good Christian women in there own way who are serving those who have no real interest in godliness and place no real emphasis on it. Nelly Dean is a realistic character in a romantic novel, while Felicite is a romanticized character in a realistic story. Nelly Dean is a servant in a household that is filled with people that are difficult to get along with. They are in constant turmoil with each other, and they almost seem to enjoy the conflict they cause. Nelly Dean is the one character that does not usually allow herself to be pulled into the conflicts that the rest of the characters embroil themselves in. She is able to stand back from the situation and give sound advice. Felicite does not seem as able to distance herself from the problems around her until she gets older and is physically unable to participate. Both women are passed from master to master because of no true faults of their own, and neither woman seems to have much control over her own destiny. While Nelly Dean stays with the same family, she has to move and get accustomed to new bosses every time some one dies. Felicite just seems to have plain bad luck in her choice of employers at the beginning of her career. In spite of this, both women seem quite satisfied with their lives, while the people who are in charge of them seem a lot less happy with their own lives. The characters in ‚"Wuthering Heights‚" frequently have severe fits of negative emotion, while Nelly quietly looks on. The only time that we see Felicite completely overcome with grief is when she thought she was going to have control, and she lost it. This happens when Felicite is still relatively young. She falls in love with a boy, and when he decides to marry some one else, ‚ÄÃ ºshe threw herself on the ground, screamed, called to the God of mercy, and moaned‚ÄÃ ¹ (1021). After this first display of emotion, she picked herself up and moved on with her life.

Embarrasing Moment

My most embarrassing moment I consider myself to be one who doesn't easily get embarrassed, but one of my most embarrassing moments happened this past summer. It all started when a few friends of mine decided that since it was incredibly hot out that summer day, that we should all go down to Tubbs hill for a swim. I’m not sure if you realize how busy downtown is during mid-summer season, but understand it’s almost always completely jammed full of people trying to fight off the blistering sun.So my friends and I hiked up the path to get a good spot to start jumping off the rocks and start swimming, but all the great spots were all full. We decided to just find a close spot and just deal with all the people in the area. Our day progressed as normally as you’d expect, and everyone was enjoying the water and how refreshing it was fighting off the heat of the day. Eventually everyone was starting to get bored jumping off the smaller rocks as well as just swimming arou nd, so my friends decided we should start jumping off the higher rocks. Eventually it came to my turn to jump and I went for it.As I dived into the water I didn’t realize at the time the sheer pressure on my swim shorts, but once I broke the surface of the water for air it struck me. I had lost my swim shorts on the dive, so I was sitting in the water completely nude in front of all my friends and random strangers that were watching. I franticly searched for my swim shorts, but to no avail, they were lost. Eventually a friend brought me a towel so I could get out of the water and return home. I would have to say that this was one of the most extremely embarrassing moments I’ve had so far in my lifetime.

The Tragic Outcome Of The Monstrous Isolation Frankenstein...

Now the final facet to discuss is the tragic outcome of the monstrous isolation Frankenstein and the Monster suffer--their demise. It is a twofold blow of a personal inability to escape isolation’s grasp coupled with zero chance of outside help because of the isolation that sends both inexorably to expiry. The Monster simply wants to, â€Å"become an actor in the busy scene where so many admirable qualities were called forth and displayed,† (130) due to the lesson he learns from the cottagers but from which he is totally excluded. So a solitary solution to his troubles is not possible to begin with. Unfortunately, in his life long search for inclusion, he is turned away from first his creator then the rest of his chance encounters with humanity due only to his monstrous form that no one could imagine could contain any human capacity for friendship, which his unnatural birth imbued him with. Even his plea for a second like him is eventually rebuked by Frankenstein, the o ne man most likely and farthest from helping him. His isolation truly sealed, the Monster is left with no purpose but to dedicate his life to torturing humanity and his creator, which leads Frankenstein to kill himself, leaving him nothing but the solace of death. For Frankenstein, it is not so simple. To begin, it is his guilt, as if for a crime, for being the man to â€Å"[turn] loose into the world a depraved wretch, whose delight was in carnage and misery,† (78) that haunts his every waking thought. Frankenstein’sShow MoreRelatedThe God Facade : A Look Into Mary Shelley s Frankenstein And The Dangers Of Playing God1209 Words   |  5 PagesThe God Faà §ade: A Look into Mary Shelley’s Frankenstein and The Dangers of Playing God. Frankenstein by author Mary Shelley is a Gothic science fiction novel written in Switzerland between 1816–1817, and published January 1, 1818. Set in eighteenth century Geneva, Frankenstein tells the story of a young man named Victor who goes away to college to study natural philosophy, chemistry, and alchemy. When armed with the knowledge he has long been seeking, Victor spends months constructing a creature