Enthalpy and Hess law

Enthalpy change and Hess's law. Introduction: Enthalpy is the total energy of a system, some of which is restored as chemical potential energy in the chemical bonds. During reactions, bonds are broken and formed. As a result, all reactions are accompanied by a change in the potential energy of the bonds, and hence an enthalpy change. This enthalpy change of reaction can be measured and is given the symbol H. The temperature of a system is a measure of the average kinetic energy of the particles present. Therefore, during a reaction, as bonds are broken and formed, there is a change in this average kinetic energy and this will result in a change in the temperature of the system. On the other hand, heat is the measure of the total energy of the substance. When the temperature of a substance increases or decreases, heat energy is absorbed or released from the environment. In order to measure this change in temperature, the following formula can be used:- Heat energy = m.C.T ......where, m= mass of the substance C= specific heat capacity T= change in temperature Aim of experiment: - This particular experiment focuses on Hess's law. Hess's law states that the total enthalpy change on converting a given set of reactants to a particular set of products is constant, irrespective of the way in which the change is carried out. For this experiment, the conversion of NaOH to

  • Word count: 1604
  • Level: International Baccalaureate
  • Subject: Chemistry
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Absorbance of light by a transition metal complex investigation

Stephanie Chan 12HT Chemistry HL - Mr. Fryer Absorbance of light by a transition metal complex investigation Introduction Commonly known as transition metals, d block elements have partially filled d sublevels in one or more of their oxidation states. It is in the first row of transition elements that the 3d sub-level is incomplete. These d block elements show certain characteristic properties such as multiple oxidation states, ability to form complex ions, coloured compounds and good catalytic properties. In terms of variable oxidation states, d block elements usually have a +2 oxidation number which corresponds to the loss of the two 4s electrons (as it is easier to lose the 4s electrons than the 3d electrons). Transition metals can have variable oxidation states because the ionization energies allow for up to two 3d electrons to be lost. Because transition metals are relatively small in size, the transition metal ions attract species that are rich in electrons - ligands (neutral molecules or negative ions that contain non-bonding pair of electrons - which when covalently bonded with and form complex ions. Because the d orbitals usually split up into two groups (high and low) in transition metal complex ions, the energy required to promote a d electron into the higher split level corresponds with a particular wavelength in the visible region, which is absorbed when

  • Word count: 1784
  • Level: International Baccalaureate
  • Subject: Chemistry
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Determining the mass of calcium carbonate obtained

Lab Experiment 2: Determining the mass of calcium carbonate obtained Purpose: The purpose of the experiment was to investigate the mass of calcium carbonate obtained from the reaction between calcium chloride and sodium carbonate. Apparatus: - Three beakers (250 - ml) - Spatula - Balance ± 0.1g - Filtration setup - Filter paper - Stirring rod - Plastic wash bottle Materials: - Sodium Carbonate - Calcium chloride - Distilled water Procedure . Weigh out 4.0g of calcium chloride (111g/mol) and dissolve in enough distilled water. 2. Weigh out 6.0g of sodium carbonate (106g/mol) and dissolve in enough distilled water. 3. Pour the sodium carbonate solution into the beaker containing calcium chloride solution. 4. Stir the mixture. Set up the filtration apparatus. Weigh the filter paper and then filter the mixture. Rinse the beaker and empty the contents in the funnel. Wash the precipitate with distilled water several times. 5. Place the filter paper with the precipitate and leave it to dry out. After it is completely dry, then weigh the dry filter paper with the precipitate. Data Table: Measurements taken in the experiment Mass of the filter paper 2.00g ±0.01g Mass of filter paper with the precipitate (after filter paper dried) 5.10g ±0.01g Mass of precipitate 3.10g ±0.01g* *The mass has an error of (±0.01) because of the reading in the mass, in

  • Word count: 983
  • Level: International Baccalaureate
  • Subject: Chemistry
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The Drop of Water

THE DROP OF WATER Jane Shores Jennifer Nguyen Meika Ellis Science 10 IB Mr. Cooper February 16th '06 .0 Aim: The purpose of this lab is to determine the volume of a drop .1 Problem: How can one, using a 1 ml pipette, ascertain the volume of one drop of water (dihydrogen oxide)? .2 Hypothesis: If you fill a 1 ml pipette with water and allow the water to drip through the opening, slowly enough to count each drop, then you can infer the approximate volume of a drop of water because according to the metric system, commissioned by the Academy of Science in 790, one millilitre of water is equivalent to one gram of water. Therefore, by using weight and the number of drops produced, one can figure out the volume a single drop. .3 Variables Independent: 1ml pipette Dependant: The approximate volume of a drop of water Controlled: The size of the drops, the volume of water placed in pipette All of the relevant variables identified in this lab are quantitative. The 1ml pipette is vital to this lab because it is the instrument that we intend to utilize to form drops of water from 1ml of water. The volume of a drop of water is the responding variable because in this experiment, we are trying to determine a successful method for discovering the volume of a drop of water, so if we can successfully determine the volume of a drop of water, then our experiment has proved my

  • Word count: 1605
  • Level: International Baccalaureate
  • Subject: Chemistry
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Water of crystallization of BaCl2.xH2O

DETERMINING THE EMPIRICAL FORMULA OF HYDRATED BARIUM CHLORIDE BaCl2 * DESIGN: Introduction: Water of crystallization is water in the structure of a crystal but not chemically bonded to the host molecule. Hydrates are compounds that contain water molecules in their solid crystalline form, e.g. CuSO4.5H2O or CaSO4.2H2O. Usually, a defined number of water molecules are associated with each unit of the primary substance. Barium chloride BaCl2 is a hygroscopic ionic chemical compound, which attracts water molecules in its surrounding environment. In this experiment, we try to determine the number of water molecules in each molecule of the sample. Question: What is the empirical formula of crystallized barium chloride BaCl2.xH2O, in other words, in what ratio is barium chloride and water in the hydrate? Hypothesis: The most common form of crystallized barium chloride is BaCl2.2H2O. It is possible that the sample barium chloride in the lab also has the same empirical formula, which means there are 2 molecules of water associated with each molecule of BaCl2. Variables: Independent variable: The mass of hydrated barium chloride (BaCl2.xH2O) Dependent variable: The mass of anhydrous barium chloride (BaCl2) Control of variables: Controlled variable Possible way of controlling The content of the crucible Make sure there is no other mass loss than the loss of water by

  • Word count: 1860
  • Level: International Baccalaureate
  • Subject: Chemistry
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The Devastating Nuclear Weapon

The Devastating Nuclear Weapons During the World War 2, America started building nuclear bombs and dropped them on the Japanese cities Hiroshima and Nagasaki. The bombs killed many people, and destroyed all the surroundings. There should be no nuclear weapons in our world because they are highly destructive, inhumane and make our world unsafe. First, nuclear weapons are highly destructive devices. When a nuclear bomb explodes it has three main effects: thermal heat, radiation and a high-speed blast wave. The temperature of the heat in the fireball of the explosion is somewhere between 1-10 million degrees Celsius. This heat spreads and burns everything in its way. Many people die from burns after a nuclear bomb explosion. The radiation is a second effect of the nuclear bomb. 'People exposure within 500 meters of ground zero was fatal. People exposed at distances of 3 to 5 kilometers later showed symptoms of aftereffects, including radiation-induced cancers.' (1) The blast is one of the most destructive effects of the nuclear bomb. '90% of the city was leveled by the 500 mile an hour wind of the blast, which charred the victims' skin two miles away and incinerated those directly below the detonation.' (2) These were the effects of the bomb dropped on Hiroshima. The bombs now are much more powerful and corrosive. Second, the nuclear bombs are inhumane. It is considered okay

  • Word count: 630
  • Level: International Baccalaureate
  • Subject: Chemistry
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Estimating the Iron(II) content in an iron tablet using a standard solution of potassium manganate (VII)

Estimating the Iron(II) content in an iron tablet using a standard solution of potassium manganate (VII) Results Table 1: Data collection - burette reading before and after potassium manganate is used to reach the end-point/ml±0.05 Trial Test 1 Test 2 Initial Reading 0 9.15 6.5 Final Reading 9 38.25 35.6 Table 2: Processed data - volume of potassium manganate used to reach end point (Volume = final reading - initial reading) Trial Test 1 Test 2 Volume used /ml±0.1 0 9.1 9.1 Calculating the amount of iron(II) present The iron was oxidized from its 2+ state to 3+ by sulfuric acid: And the manganate iron was reduced as follows: This half equation is balanced as follows: Since the above equation involves the transfer of five electrons, the equation involving iron needs to be multiplied by five before the two half equations can be added together: Adding the two half equations: This simplifies to: This equation shows that for every five present, one is required for the reaction to be completed. 9.1ml of potassium manganate solution was used for titration. From this the amount of manganate ions used can be calculated as follows: Amount of present = Mass of present = Since the volume of solution used was 25cm3, one-tenth of the total solution made from the five iron tablets, the above calculation shows that: . Dividing this value by 5, we get

  • Word count: 823
  • Level: International Baccalaureate
  • Subject: Chemistry
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Mass-Mass Relationships

Mass-Mass Relationships Introduction: A mass of any product and reactant in a chemical equation can be found by only knowing the mass of one reactant/product. The mass of the known substance is turned into moles, and by using the mole ratio, the number of moles of the unknown substance can be calculated. This number is then switched into the mass by multiplying it by its molar mass. In the following experiment, 3 grams of sodium carbonate, Na2CO3 is measured out and then an excess of 10% of HCl would be added to make sure the sodium carbonate react completely. Na2CO3 (s) + 2HCl (l) › 2NaCl (s) + H2O (l) + CO2 (g) By knowing the mass of the sodium carbonate reactant, the mass of sodium chloride product can be calculated by using the mass-mass relationship including the use of the mole ratio between them. This experiment is carried out to prove this mass-mass relationship correct between sodium carbonate and sodium chloride Aim: To prove the mass-mass relationships by measuring the amount of sodium chloride produced Apparatus: - One 150 cm3 Beaker - 100 cm3 Graduated Cylinder - Bunsen Burner - Heat Proof Mat - Tripod - Gauze - Safety Goggles - Balance to 0.01 g Reagents: - 1.0 M HCl Solution - Solid Na2CO3 Hypothesis: I think 3.31 gram of sodium chloride will be produced. Method: . Weigh the mass of a clean, dry 150 cm3 beaker to the nearest

  • Word count: 551
  • Level: International Baccalaureate
  • Subject: Chemistry
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Investigate the effect of one factor on the boiling temperature of a liquid

Investigate the effect of one factor on the boiling temperature of a liquid Background Information Salt (NaCl) is a substance with a low vapour pressure. In comparison to any type of liquid, salt still has a lower vapour pressure. If salt was to be dissolved in water (H2O), in this case for the experiment, then consequently the salt will cause the overall vapour pressure of the solution to decrease and have a lower vapour pressure. Lowering a solution's vapour pressure means that the solution will have a higher molecule vaporising point then pure water (without added salt). In other words, the boiling point of the solution will increase and therefore have a higher boiling point temperature. A term used to describe this outcome is also known as boiling-point elevation. [1] In this experiment the affect of table salt on the boiling point of tap water will be measured. Pure tap water without table salt added will be the control of this experiment and all results will be compared to the results of the pure tap water. The temperature of the water will be measured in degrees Celsius (°C) and the amount of table salt added will be measured in grams (g). This experiment will be carried out at Standard Lab Conditions (SLC); Research Question: How does table salt affect the boiling point of water? Hypothesis: It is hypothesised that adding table salt will cause the water to

  • Word count: 1230
  • Level: International Baccalaureate
  • Subject: Chemistry
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How Changing Molarities Effect Percentage Yield

Design Lab Report Question How will varying the molarity of excess HCl to 1.0M, 2.0M and 3.0M affect the percentage yield of CO2 in the following reaction: CaCO3+ 2HCl› CaCl2+ CO2+ H2O Materials and Apparatus 50mL of 1.0M Hydrochloric acid, 75mL of 2.0 Hydrochloric acid, 50mL of 3.0M Hydrochloric acid, Calcium carbonate, 3 250mL beakers, 1 250mL graduated cylinder, 3 stirring rods, masking tape, balance. Variables Independent: Concentrations of HCl Dependent:The percentage yield of CO2 Controlled: Mass of CaCO3, size of beakers, balance Controlling Variables Mass of CaCO3: 3.0g will be used in each trial Size of beakers: the same beaker will be used in most of the trials Balance: the same balance is used in all trials Procedure: See attached sheet. Diagram of Apparatus: Data Collection and Processing Raw Data Tables Table 1: Trial 1 Mass of beaker before addition of CaCO3 (g) Mass of beaker after addition of CaCO3 (g) 3.0M 62.53±0.005 63.99±0.005 2.0M 76.32±0.005 77.81±0.005 .0M 264.80±0.005 266.30±0.005 Table 2: Trial 2 Mass of beaker before addition of CaCO3 (g) Mass of beaker after addition of CaCO3 (g) 3.0M 10.02±0.005 11.59±0.005 2.0M 27.90±0.005 29.50±0.005 .0M 260.66±0.005 262.26±0.005 Table 3: Trial 3 Mass of beaker before addition of CaCO3 (g) Mass of beaker after addition of CaCO3 (g) 3.0M

  • Word count: 795
  • Level: International Baccalaureate
  • Subject: Chemistry
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