The change in enthalpy for the combustion of magnesium metal Abstract ======== 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. Compared with the accepted value of –601.8 kJ/mol Mg, our experimental error was 2.46%. Introduction In this investigation the change in enthalpy will be determined from the following equation: 2Mg + O2 ® 2MgO, but in an indirect manner. Magnesium metal burns with a bright extremely hot flame to produce magnesium oxide. It would be difficult to measure the heat of the reaction since the reaction is rapid and occurs at a high temperature (LeMay et al, 1996). So, to determine the change in enthalpy we will employ Hess’s Law of heat summation: It states that the value of DH for a reaction is the same whether it occurs directly or as a series of steps (LeMay et al, 1996). We will perform the two following reactions: Mg + 2HCl ® MgCl2 + H2 and MgO + 2HCl ® MgCl2 + H2O, determine their enthalpy changes (DHs), and they will then be “added” to that of a given equation, the combustion of water, H2 + 1/2 O2 ® H2O DH=-285.5 kJ/mol. In this investigation we will be working with potentially dangerous chemicals and safety precautions must be made. Magnesium oxide is a respiratory and eye irritant, the dust must not be inhaled and all work with MgO should be conducted in the fume hood ( Cartwright,... ... middle of paper ... ...te, only having a 2.46% error. These errors may be accounted for by inaccurate measurements, mathematical mistakes, incomplete reactions, poor heat collection, incorrect recording of data, and poorly calibrated tools. To avoid such error one should label all materials, check each tool before use, take extra care in reading and recording of measurements, double check all calculations, and most of all be patient, labs take time and a rushed procedure leads to inaccurate data and incorrect analysis. Sources Cited Cartwright, H.(last revised 2002, November 5). Chemical and other Safety Information. The Physical and Theoretical Chemistry Laboratory, Oxford University. [online]. (accessed 2002, December, 4) LeMay, H.E.,Beall, H., Roblee, K.M., and Brower, D.C. (1996).Chemistry: Connections to our changing world, Laboratory Manual. Upper Saddle River, NJ: Prentice Hall.
The first step that we took to accomplish our goal was to put on our safety goggles and choose a lab station to work at. We received one 400ml beaker, one polyethylene pipet, two test tubes with hole rubber stoppers, two small pieces of magnesium (Mg), one thermometer and a vial of hydrochloric acid (HCl). We took the 400ml beaker and filled it about 2/3 full of water (H20) that was 18 OC. Then we measured our pieces of Mg at 1.5 cm and determined that their mass was 1.36*10-2 g. We filled the pipet 2/3 full of HCl and poured it into one of the test tubes. Then, we covered the HCl with just enough H2O so that no H2O would be displaced when the stopper was inserted. After inserting the stopper, we placed the Mg strip into the hole, inverted the test tube and placed it in the 400ml beaker. HCl is heavier than H2O, so it floated from the tube, into the bottom of the beaker, reacting with the Mg along the way to produce hydrogen gas (H2). We then measured the volume of the H2, cleaned up our equipment and performed the experiment a second time.
In communist China, prior to the population boom, more people meant more manpower to create more economic prospects for the communist nation. The communist government condemned birth control and banned imports of contraceptives (Attane, 2002). Lack of birth control, and government encouragement led China into a time of vast population increase. Hundreds of millions of extra children were born in a baby boom that sent the birth rate soaring to 5.8 children per couple, a level considered unsustainable (Cai & Lavely, 2003). With an increasingly growing population, food sources began to become depleted, and soon it became clear that the rate of reproduction needed to be decreased. To begin, government propaganda cropped up, pushing the sloga...
Convection is a transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy along with its mass. According to Oxford Dictionary, convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder or denser material to sink under gravity's influence, that results in transfer of heat. Two fluids are liquid and gas.The fluid above a hot surface expands, becomes less dense, and rises.This applies to objects such as steam from a hot cup of coffee turning cool, ice melting like heat moving to ice from the air, or frozen material becoming raw like how frozen food thaws more quickly under cold running water. When
Out Of This FOurnace, written by Thomas Bell, takes historical context about the difficulties of immigration. It outlines the story of immigrants that line three generations. It shows how people want to improve their lives and will take measures in doing so. This novel shows how hard working conditions are for this family and how it was dealt with.
Investigation of the heat energy produced by combustion of various alcohols. Aim: ---- To investigate how different alcohols produce different amounts of heat energy through combustion. I will be heating water using different alcohols as fuels and measuring the amount of fuel consumed.
According to (Pittman, Keiley, & Kerpelman, 2011), Bowlby theorized that it is the interactions between people that form connections and develop attachments. There are four different types of attachments; secure, avoidant, and anxious ambivalent. When we look at this theory applied to children we see that a secure attachment is when children are most comfortable when their parents are around and are easy to soothe by the parents. Insecure or avoidant attachment is when the child doesn’t prefer to be near the parents and could care less if the parents are absent. This happened when the parents failed to meet their child’s needs, despite a child expressing their needs. Anxious ambivalent attachment is when the child won’t leave their parents side, even if it is to explore their surroundings, is distraught if the parents leave, and mistrusting if the parents try to comfort after leaving (Arnett, & Maynard,
one gram of water by 1ºC. I chose to use water because it is safe,
Being an ethnic Chinese made me feel interested in the Chinese current situation. According to my research, one out of five of the world’s population lives in China, how can a country have that tremendous population, which is about 1.4 billion people? We have known that overpopulation is not a good thing to be happened in a country, especially in a LEDC. So, did the country government put any effort on controlling the population?
be yes as I will then be able to use enthalpy change of reaction to
(g) Change in mass (g) Methanol 20 170.00 167.08 2.92 Ethanol 20 170.00 167.77 2.23 Propan-1-ol 20 170.00 168.03 1.97 Butan-1-ol 20 170.00 168.16 1.84 Pentan-1-ol 20 170.00 168.24 1.76 Having found these results I then worked out the combustion per mole of alcohol. Alcohol Mass of water heated (g) Heat evolved during reaction (J) Change in mass of burner (g) Combustion of one mole of alcohol (kJ/mole)
The Effect of Temperature of Hydrochloric Acid on the Rate of Reaction Between Hydrochloric Acid and Magnesium
The center of the Earth is composed of a solid metallic core surrounded by a molten layer of liquid metal. This paper will discuss the reasons to believe the theory that the Earth has a molten core, and the important discoveries that have led to this generally accepted theory. It is very reasonable to agree with this theory when paying credence to the logical evidence that answers questions about the Earth’s core. This evidence includes information about the elemental make up of the Earth, the reason for the Earth’s magnetic field, and some of the possibilities of the Earth’s formation.
Thermodynamics is the branch of science concerned with the nature of heat and its conversion to any form of energy. In thermodynamics, both the thermodynamic system and its environment are considered. A thermodynamic system, in general, is defined by its volume, pressure, temperature, and chemical make-up. In general, the environment will contain heat sources with unlimited heat capacity allowing it to give and receive heat without changing its temperature. Whenever the conditions change, the thermodynamic system will respond by changing its state; the temperature, volume, pressure, or chemical make-up will adjust accordingly in order to reach its original state of equilibrium. There are three laws of thermodynamics in which the changing system can follow in order to return to equilibrium.
The first law of thermodynamics is that heat is work and work is heat. Energy can’t be created or destroyed but it can be converted from one form to another form. First law of thermodynamics would be eating food. Humans turn food into chemical energy and humans need that energy to keep functioning. The second law of thermodynamics is heat can only transfer to colder objects not hotter objects. An example would be ice melting in a cooler. The coldness from the ice doesn’t leave the cooler, instead the heat transfers into the cooler to melt the ice. The third law is that the work or energy put in is equal to the work out plus heat. Some heat energy will always be wasted, such as a computer giving off heat. Using the first law, when the energy is transferred from one form to another, there will always be wasted heat because of the second law. This is because the energy is converted from a useful form to a less useful form. The less useful form is heat.
MIG welding, the most preferred and most efficient way of welding today’s vehicles, because of the more heat-sensitive metals and the use of thinner gauge this type of welding is recommended in all body shops.