The enthalpy change of a reaction Essay Example for Free

The enthalpy change of a reaction Essay This is the equation for the reaction I intend to find the enthalpy change for. As this particular reaction is very difficult to measure the enthalpy change by carrying it out (the decomposition of CaCO3 needs a temperature of over 800i C), I must use another method and it uses Hess Law. Hess Law States: The enthalpy change for any chemical reaction is independent of the intermediate stages, provided the initial and final conditions are the same for each route. CaCO3 CaO + CO2 CaCl2 + CO2 + H2O. In simpler terms, the main point of Hess Law is that the total enthalpy change for the indirect route of a reaction is the same as the direct route, i. e. ?H1 = ? H2- ? H3. The diagram above represents a Hess Cycle or a Thermochemical Cycle. By knowing the enthalpy changes in two parts of the cycle, it is possible to calculate the third part and complete the cycle. This is how I am going to carry out my experiment. For my experiment I will: 1. ) React calcium carbonate with hydrochloric acid. 2. ) React calcium oxide with hydrochloric acid. In both of these reactions I will measure the enthalpy changes by recording the starting temperature and following the reaction, the end temperature. By following this procedure, I can calculate the change in temperature and consequently the enthalpy change. The apparatus I will need for these reactions includes: 2 x Polystyrene Cups 250ml Beaker Digital Thermometer 50ml Measuring Cylinder I decided to use a polystyrene cup so I could reduce heat loss polystyrene is an insulator, whereas if I had used glass heat loss would have been a huge influence on results. I am using a beaker so that when I need to move the reactants, I do not influence any temperature change just through my body heat. Also, the thought of the solution spilling was not a pleasant one, so in case of spillage, the beaker would catch it. The digital thermometer is much more accurate than a conventional thermometer because it reads down to 1 decimal point. Safety Apparatus: Safety glasses and lab-coat. The quantities of materials I have available: HCl (2. 0 mol dm-3) : As much as required CaCO3 : Between 2. 4g and 2. 6g CaO : As much as required. In order to determine the quantities I will need to use in the experiment, I must carry out a few simple calculations. Here is the equation for the first reaction I will carry out, involving CaCO3 and HCl. CaCO3 + 2HCl CaCl2 + H2O + CO2 This equation shows that 2 moles of HCl are needed for every 1 mole of CaCO3 to react. Using this information I can calculate the volume of HCl I will need in the reaction. I first need to find the number of moles of CaCO3 will be in the reaction: Number of Moles = Mass Relative Formula Mass No. of moles of CaCO3 2. 5g 100 0. 025 moles of CaCO3 Now I need to calculate the minimum amount of HCl I will need in the reaction. (Adding more would not affect the results because rate of reaction has no relevance to the experiment. All that is important in this reaction is that it is completed. ) Volume = Moles Concentration Volume of HCl 0. 05 (twice as many as CaCO3, as required) 2 0. 025 dm3 of HCl I now know that the quantities I require, in the first experiment, are as follows: CaCo3 About 2. 5g HCl 50cm3 (25cm3 is minimum any less will affect results). In the second reaction, involving Calcium Oxide and Hydrochloric acid, the equation is: CaO + 2HCl CaCl2 + H2O Again, like the first reaction, 2 moles of HCl are required to react with 1 mole of CaO. To keep things simple, I am going to use the same number of moles of CaO as CaCO3. Mass = Moles x Relative Formula Mass Mass of CaO needed = 0. 025 x 56 1. 4g Volume of HCl needed 0. 05 (twice as many as Ca0, as required) 2 0. 025 dm3 In order to carry out these experiments, the following directions should be carried out carefully. Method for reaction 1: CaCO3 and HCl. Add 2. 5g of CaCO3 to a polystyrene cup.   Place the polystyrene cup in a beaker.   Add 50cm3 of HCl to a 50ml measuring cylinder. Measure the temperature of the HCl.   Add the HCl to the CaCO3 and measure the end temperature. Once I have measured the end temperature I will compare it to the start temperature and calculate the temperature change. Method for reaction 2: CaO and HCl Add 1. 4g of CaO to a polystyrene cup. Place the polystyrene cup in a beaker.   Add 50cm3 of HCl to a 50ml measuring cylinder.   Measure the temperature of the HCl. Add the HCl to the CaO and measure the end temperature. Again, once I have measured the end temperature I will compare it to the start temperature and calculate the temperature change. Once the temperature changes have been calculated ? H needs to be found. Once all of the enthalpy changes have been calculated, follow the equation ? H1= ? H2- ? H3 Risk Assessment The substances which I am using are both fairly dangerous and have the potential to cause serious damage. Hydrochloric acid can cause burns and is irritating to the respiratory system. The molarity I am using is only irritant but this is still not pleasant. The only form of protection that is really needed while using HCl is to wear safety glasses. Calcium oxide causes burns and is irritating to the eyes, skin and respiratory system. Again, only eye protection is really needed with the use of this substance. By using my plan, I expect to get accurate and consistent results as I have calculated the exact amounts of substances needed and factors which will affect results, such as heat loss. Nothing in my experiment will give inaccurate or varied results as long as the method is followed strictly, i. e. correct and precise measurements of substances. The only way the experiment can be inaccurate therefore is through human error. Sources used in devising my plan:   Haz-Cards. Chemical Ideas, Second Edition Burton, Holman, Lazonby, Pilling, Waddington.   Class work notes Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Patterns of Behaviour section.

The Cuban Revolution Essay examples -- Cuban History, Fidel Castro,

After year of recruiting, training, plotting, Fidel was ready to launch his revolutionary offensive. â€Å"His rebel ‘army’ consisted of less than 200 men, and two women;† (Huberman 1960: 28) the group consisted of students or graduates, and nearly all of them were young people like himself and his brother, Raà ºl. Most of them were â€Å"politically active, articulate and impatient young men who had been drawn to the radical movements or to the ardently reformist Orthodox Party of Eduardo Chibas.† (Macgaffey 1962: 275) The rebels gathered outside Santiago, in the Fidel’s native Province of Oriente where they could launch an attack on Moncada Barracks, the army’s second largest military installation. (Huberman 1960: 28; Macgaffey 1962: 275) The attack was slated for July 26, 1953, at dawn, during the annual carnival celebration. (McCormick 1998: 67) â€Å"With the carnival in full sway, Castro expected the military to have its guard down.† (Leonard 1999: 9) At dawn of July 26, they divided into small groups to launch the assault, each group with specific objectives. The first intention was to â€Å"take by the surprise and capture the Fort Moncada, and take machine guns, tanks, armored trucks, up-to-date rifles and ammunition.† (Huberman 1960: 28) They could then seize radio stations, (Hampsey 2002: 95) and â€Å"They were to announce a revolution based on ‘Creole values,’ (Goldenberg 1965: 151) led by new men ... free of all obstacles with foreign nations and ... of appetites of politicians. They promised welfare and economic prosperity, social justice, respect for other nations, and respect for the constitution.† (Macgaffey 1962: 275, 276) â€Å"Such publicity was designed to call the people to revolt against the dictator, Batista,† (Hampsey 200... ... arrange a Military Junta.† (Goldenberg 1965: 163) However, before the plan could be put into operation, ‘the battle of Santa’ Clara took place, ending in a total fiasco for government troops.†(Goldenberg 1965: 163; Macgaffey 1962: 293) On the night of December 31, Batista and his collaborators fled to Dominica Republic. (Macgaffey 1962: 293) Immediately, Fidel called for general strike and subsequently, other major cities surrendered and Fidel and his rebels marched to Havana. (Goldenberg 1965: 163; Macgaffey 1962: 293) â€Å"Before the dawn on January 2, Fidel’s army marched into Santiago, and accepted unconditional surrender of Batista’s forces at Moncada.† (Goldenberg 1965: 163) The war was over and Fidel and his victorious army rode in triumph from one end of the island to the other and arrived in Havana on January 8. (Goldenberg 1965: 163; Macgaffey 1962: 293)

Mob Mentality

Mob mentality, or mob psychology, has been observed in numerous rock concerts and sports events in the United States, which often ends in riots and numerous people trampled to death. These events imply that there are certain influences exerted by a group that affect a person's behavior (Waddington & King, 2005). The effect of these observations is the conduct of many studies and theories in the field of social psychology.As early as 1895, Le Bon, who was writing about crowd psychology, published his work entitled, The Crowd: A Study of the Popular Mind. His work posits that people who form a large crowd lose their conscious personalities, and these are â€Å"replaced by a sinister uncivilised and potentially barbaric ‘collective mind (Waddington & King, 2005).’†The concept of mob psychology is rooted on the idea that the persons involved are burdened with an incapacity for self-control. Thus, these people who are susceptible of being part of the mob easily succumb to pressures, influences, and temptations (Feasibility and Admissibility of Mob Mentality Defenses, 1995).The perceived reason underlying mob mentality is classified into three complementary mechanisms. First among these is anonymity. A person who usually acts as a distinct person is prevented from behaving badly because his actins would be associated with himself alone. However, a person who loses his personality and becomes merely a part of large crowd becomes anonymous, making him feel liberated from personal responsibility from their actions (Waddington & King, 2005).Another mechanism involved in crowd disorder is suggestibility. Le Bon asserts that people in a group become â€Å"less resistant to the ‘hypnotic’ powers of suggestion.† Thus, the mob is compelled into engaging in abnormal and unsavory behavior. This mechanism suggested by Le Bon is built upon by Allport in 1924, who suggested that mob psychology involves â€Å"social facilitation† where by mutual stimulation causes the overriding of customary self-restraint exercised by people in normal circumstances (Waddington & King, 2005).  Finally, there is contagion. This mechanism refers to the fact that the â€Å"†high emotions spread contagiously† as if such effect is inevitable. This leads to the often-observed violent frenzy of mobs (Waddington & King, 2005).Mob mentality is a defense against criminal liability, and is based on psychological theory. In technical terms, it is referred to as Mob Violence Proclivity Syndrome. It belongs to other psychological defenses to criminal liability, such as child sexual abuse syndrome and rape trauma syndrome (Feasibility and Admissibility of Mob Mentality Defenses, 1995).The idea is that group criminal behavior is explained by the tendency of humans to get caught up in the excitement of situations and people such that they are unable to make meaningful, real, and rational decisions about their behavior (Feasibility a nd Admissibility of Mob Mentality Defenses, 1995).The legal community has observed the effects of an understanding of this human behavioral tendency on public policy, the law, and criminal liability. Whereas in the old times, crimes committed by a group had been made graver by the fact that several people participated in the act, nowadays, such fact is used to mitigate criminal liability of the offenders.Thus, the fact that people who merely followed the mob did not have the opportunity to make rational choices about their actions is enough to help them negate or avoid criminal responsibility for their acts (Feasibility and Admissibility of Mob Mentality Defenses, 1995). This particular effect of the psychological concept of mob mentality raises serious concerns on public policy and the law.ReferencesFeasibility and Admissibility of Mob Mentality Defenses. (1995). Harvard Law Review 108(5),   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   1111-1126.Waddington, D. & King, M. (2005). The Diso rderly Crowd: From Classical PsychologicalReductionism to Socio-Contextual Theory – The Impact on Public Order Policing   Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚  Ã‚   Strategies. The Howard Journal 44 (5), 490–503

Animated Voice Images Of Tsunamis - 1031 Words

Animated voice: Footage of tsunamis. https://www.youtube.com/watch?v=vYy2h8IUV1U Yesterday afternoon, at approximately 14:46 JTS time, a massive 9.0 magnitude earthquake occurred just off the east coast of Japan, across from Sendai. The epicentre of the earthquake was at 38.322 °N 142.369 °E and caused a massive tsunami to form. Now we’ll go over to our very own reporter, Willow Jones, who will be explaining tsunamis for you. Willow: Live footage from studio. Hello, I’m Willow and I will be your reporter for tonight. Now, over 90% of tsunamis are caused by underwater earthquakes like this one. The other causes of tsunamis are underwater landslides, volcanos, and even meteorites! Earthquakes are caused by the movement of tectonic under†¦show more content†¦This goes on like a Mexican wave. When the energy reaches the surface, and has nowhere else to go, it translates outwards like a soundwave. Tsunamis can travel incredibly fast, as fast as 800km an hour! The longer it takes to reach land, the stronger the tsunami gets. Photo of the ring of fire. https://www.google.com.au/search?q=nuclear+disasterssafe=strictbiw=1536bih=690source=lnmstbm=ischsa=Xsqi=2ved=0ahUKEwj00teW1MzOAhUDl5QKHQp_DAAQ_AUIBigB#safe=stricttbm=ischq=ring+of+fireimgrc=De4mj2rYdEQ0_M%3A Early warning systems are installed at intervals on the ocean floor, especially around the ring of fire, where many earthquakes occur. Footage of tsunami. https://www.youtube.com/watch?v=S2ZOmMH4WHA#t=0.3316559 When a tsunami reaches the coastline of a country, the preliminary wave comes and acts like a sudden high tide. This wave then quickly disappears back into the ocean. This action provides an early warning system, letting people that in a few minutes the real tsunami wave is coming. When the real tsunami wave arrives, it will knock anything down that is in its path. Cars, people, and even buildings in the case of a large tsunami, will be pulled down. Although there are early warning systems, the message does not get out quick enough and many people are unaware that a tsunami is soon to come. Now we will go over to former nuclear reactor manager and scientist, Will Morgen, to explain