Chemical monitoring and management - composition of the atmosphere and the problems of pollution.
Chemical monitoring and management Part A . describe the composition and layered structure of the atmosphere. First of all the atmosphere is a blanket of air which surrounds the earth. The atmosphere has many functions to maintain life on earth. This includes protection of UV radiation, vacuum of space and is part of the process of photosynthesis. There are 4 different layers in the atmosphere of the earth. All of these layers have been recognised due to the chemical composition, the density and thermal composition. Troposphere The troposphere is the first layer of the atmosphere starting from the surface of the earth. It extends about 15 km upwards from the surface of the earth. In this layer the temperature drops from 17 to -52 degrees. 90% of earth's gases are present in the troposphere. The upper region of the troposphere is very stable. This region is called the tropopause. This region helps in reducing the mixture of gases. Stratosphere In this layer the ozone of the earth is present. Hence the temperature of the stratosphere increases to about -3 degrees due to the hot UV radiation present in this region of the atmosphere. Thus this region compared to the troposphere is very dry. The Stratosphere extends from the top of the troposphere for about 31 miles. Many jet aircrafts fly in the stratosphere because it is very stable Mesosphere The mesosphere starts
Design Lab, HCl + Marble chips
Sagar Sood IB Chemistry HL Yr. 2 Ms. Rachel 30th Jan, 10 Introduction How does change in concentration of HCl affect the mass of carbon dioxide evolved in the reaction: CaCO3 + 2HCl --> CaCl2 + H2O + CO2 Increasing the concentration of an acid increases the number of collisions per second between particles, therefore, the rate of reaction increases. The more concentrated the reactants (in this case, it is hydrochloric acid), the more collisions per seconds occur between the particles, hence creating more mass of products in less time. The reaction will start faster in comparison to the rate at the end of the reaction. This is because when the two reactants are first mixed, their concentrations are both at their highest. As the experiment goes on, the concentration of the reactants will decrease, so the reaction will slow down until it finally comes to a stop. Independent Variable: Concentration of HCl (mol L-1) Dependant Variable: Mass of CO2 (grams) Controlled Variables: > The mass of marble powder (grams) - if the total mass of the marble powder is varied, the reaction will not be a fair test, so the mass must be kept the same to 2.00g ± 0.01g > Volume of acid (mL) - although the amount of hydrochloric acid needed to neutralize the marble powder differs according to the strength of the acid, the volume must be kept the same so as to make it a fair test. In
fizzy drinks
Aim The aim of the experiment is to check whether pH of the chosen fizzy drink is basic, neutral or acidic. To find the answer the titration method will be used. The chosen fizzy drink will be Sprite due to its transparency (it is easy to see when the color changes during the experiment). Hypothesis Sprite will probably have acidic pH (smaller than 7) as one of ingredients is citric acid. However as it is drink used by people pH cannot be to small as it would be harmful to the human organism. As I checked pH of Sprite should oscillate somewhere around 2.75. Theory "A titration is a method of analysis that will allow you to determine the precise endpoint of a reaction and therefore the precise quantity of reactant in the titration flask. A buret is used to deliver the second reactant to the flask and an indicator or pH Meter is used to detect the endpoint of the reaction. A typical titration begins with a beaker or Erlenmeyer flask containing a precise volume of the reactant and a small amount of indicator, placed underneath a burette containing the reagent. By controlling the amount of reagent added to the reactant, it is possible to detect the point at which the indicator changes colour. As long as the indicator has been chosen correctly, this should also be the point where the reactant and reagent neutralise each other, and, by reading the scale on the burette, the
A study of trends in period 3
Lab Experiment 3: A study of trends in period 3 Purpose: The purpose of the experiment is to study the trends in properties of the oxides and chlorides across the third period of the periodic table. Apparatus: - Eye protection. - 1 rack + 4 test tubes - Full range indicator paper. - Samples of the following oxides: NaOH, MgO, Al203 - Samples of the following chlorides: NaCl, MgCl2, AlCl3, PCl5 - Hot plate - 500 ml beaker with water Procedure . Fill 3 test tubes with about 3cm3 of distilled water. 2. Add a very small measure of each oxide to the test tubes. 3. Test the pH of each solution obtain from each oxide by using a full-range indicator. 4. Record the results in the data table. 5. Repeat the same steps except this time use the sample of chlorides instead of the oxides. Data Table 1: Properties of the oxides in period 3 Oxide Formula NaOH MgO Al2O3 State at room temp (s) (s) (s) Appearance White solid White powder White precipitate Volatility low low Low Conductivity of molten oxide Good good Good Solubility in water Soluble soluble Insoluble pH of solution in water 4 9 7 Classification of oxide(acidic, basic or amphoteric ) Basic Basic Amphoteric Structure of oxide (simple molecular, giant molecular, giant ionic) Giant ionic lattice giant ionic lattice Ionic/covalent Data Table 2: Properties of the chlorides in
Chemistry Design Prac Electrical Conductivity of Salt Solutions
Investigate the electrical conductivity of salt solutions Aim To determine whether the concentration of sodium chloride in solutions affects the electrical conductivity of the solution Background Electrical conductivity is the ability to carry out the flow of an electric current. In solutions, this depends almost entirely on the solute present. Ions are capable of carrying an electrical current. When sodium chloride (NaCl) is dissolved into water, Na+ and Cl- ions are formed, which are able to conduct electricity. Electrical conductivity is measured in microSiemens per centimetre (µS/cm) Table 1|Chemical Properties of Sodium Chloride Solution Solution Property Description Sodium Chloride Solution (NaClaq) Appearance Clear, colourless solution Odour Odourless pH 6.7-7.3 Stability Stable Flammability None Reactivity None Defining Independent and Dependent Variables Table 2|Defining the Independent and Dependent Variable Independent Variable The concentration of sodium chloride in solution - 0.0 mol dm-3 - 0.1 mol dm-3 - 0.5 mol dm-3 - 1.0 mol dm-3 - 1.5 mol dm-3 - 2.0 mol dm-3 Dependent Variable The change in electrical conductivity in the sodium chloride solution, measured in Volts using a Voltmeter. Controlling Variables Table 3|Variables and Method of control Type Variable Method of control Why is it to be controlled Controlled
Pka of ethanoic acid
Determining the pka value of ethanoic acid A titration is a procedure that can be used in analytical chemistry to determine certain value or concentration of a substance. The aim of this experiment is to determine the pka value of ethanoic acid. Every acid has its own specific dissociation constant, ka, which measures the strength of the acid. pka is equal to the negative logarithm of ka .In order to determine the pka constant for ethanoic acid it was titrated with NaOH. The reaction is as below CH3COOH + NaOH (aq) › CH3COO- + Na+ + H2O ka = [CH3COO-][H+] [CH3COOH ] pka = - log ka Materials: - NaOH (0.1 mol dm-3), CH3COOH (0.1 mol dm-3), pH meter, stand, clamp, thermometer, beakers, pipette, magnetic spin, titration pipette. Methods:- . 25 ml of ethanoic acid was poured into a beaker and placed below the titration pipette. 2. Then the pH meter was calibrated and placed in the beaker to measure the initial pH. 3. 25 ml of NaOH was poured into the titration pipette. 4. Then 1 ml sodium oxide was allowed to pour into the beaker. A magnetic spin was placed in the beaker to facilitate the reaction. 5. The change in pH was recorded. Results:- Table 1. Change in the pH value of Ethanoic acid as 25 ml of NaOH is added to it. Volume of NaOH (±0.05) (ml) pH (±0.01) Volume of NaOH (±0.05)(ml) pH (±0.01) 0 2.32 3 5.21 3.25 4 5.47 2 3.62 5 5.89
Energetics Design Lab
Rammy Abssi Chemistry - 11 May 04, 2009 Energetics Planning Lab Research Question: How does the strength of the acid, affect the change in temperature of a reaction with sodium carbonate (acid-base reaction)? Hypothesis: I believe that if acid is stronger, than the change in temperature of the acid-base reaction will be greater. Variables: Type of Variable Variable Range of Values/Method of Control Independent Variable Strength of Acid (Type of Acid) From 0.30g to 1.80g in increments of 0.30g Dependent Variable Change in Temperature Read from thermometer at the peak of reaction Controlled Volume of Acid Used 50cm3 in all trials Initial Temperature All reactions start off at room temperature (21°C - 22°C) The Base Which the Acid is Reacted With Sodium Carbonate Na2CO3 Materials: * Copper cup * Styrofoam cup * Lid for copper cup * Total of 31.80 grams of sodium carbonate (± 0.005g) * 150ml hydrochloric acid (± 0.5ml) [50ml each trial] * 150ml sulfuric acid (± 0.5ml) [50ml each trial] * 150ml ethanoic acid (± 0.5ml) [50ml each trial] * Balance (± 0.005g) * Thermometer (± 0.5°C) * Stirrer Diagram: Method: There will be three trials for each of the three different types of acids. Using 9 weighing boats split the sodium carbonate into 6 sets of 2.65 grams and 3 sets of 5.30 grams. Hydrochloric Acid: Na2CO3 + 2HCl --> 2NaCl +
The preparation of Benzoic acid from benzamide
EXPERIMENT ( 4 ) Topic : The preparation of Benzoic acid from benzamide Introduction : The preparation of benzoic acid from benzamide is a hydrolysis. In this experiment, you are requested to prepare and purify benzoic acid by some techniques. Chemicals : Benzamide, Dilute NaOH, Dilute HCl Procedures : 1. Weigh out 3 g of benzamide. Place it in a 100 cm3 (or larger) conical flask and add to it 50 cm3 of dilute sodium hydroxide solution. 2. Fit the flask with a cork carrying a glass tubing and boil the mixture for about 15 minutes. Test the gas evolved at the open end of the glass tubing when the mixture begins to boil. 3. Allow the reaction mixture to cool and then transfer it to a 250 cm3 beaker. Add an excess of dilute HCl with a dropper, swirling continuously until a copious amount precipitate is obtained. 4. Filter the resulting solution under suction, wash the crystals thoroughly with a minimum amount of ice cold water. 5. Recrystallise the crude solid from boiling water, filter to obtain pure crystals of the product. 6. Dry these crystals thoroughly between filter paper until no further sign of dampness is seen on the paper. Inspect the shape of the crystals using a hand lens. Measure the mass of the product. 7. Using the melting point apparatus, determine the melting point of your product. Results : Gas evolved =
An Experiment to Determine the Empirical Formula of Lead Iodide
An Experiment to Determine the Empirical Formula of Lead Iodide Aim: The empirical formula shows the simplest whole number of ratio of atoms of each element in a molecule of a compound. In this experiment, we will determine the empirical formula of lead iodide. An insoluble lead iodide compound is formed by dissolving the lead in nitric acid and reacting with potassium iodide. Then, the lead iodide is filtered and dried for a week. In the end of the experiment, the mass of lead, filter papers and filter paper with lead iodide are recorded. The ratio of moles of lead to moles of iodine in the compound can be obtained either by weighing/calculating the mass of each element from the experiment raw data. In order to get the mass of iodide in the lead iodide compound, we can calculate by deducting the initial mass of lead from the mass of the precipitate. By knowing the mass of each element, we can determine the amount of each element (moles) than the ratio of the compound. . Variables: Controlled 30 cm3 3M HNO3 ; distilled water ; 1.2g potassium iodide (KI) Independent Amount of Lead (Pb) Dependent Amount of lead iodide formed Method for controlling variables: Glassware, electronic balance Materials: Equipment: - 3 x 250 cm3 beaker - 1 x 150 cm3 beaker - 3 x watch glass - 1 x Electronic balance (300 g, readability ±0.001 g) - 3 x cartridge burner - 3 x
pKa. When constant successive portions of Sodium Hydroxide are added to Acetic Acid; how do the changing amounts of Sodium hydroxide mixed with Acetic Acid in the conical flask affect the pKa of Acetic Acid?
Aspect 1 Research Question: When constant successive portions of Sodium Hydroxide are added to Acetic Acid; how do the changing amounts of Sodium hydroxide mixed with Acetic Acid in the conical flask affect the pKa of Acetic Acid? Background Research: A weak acid is defined as being an acid that does not donate all of its hydrogen ions in a solution (Neuss, 2007) A weak acid represented by HA will always be in equilibrium with its ions in an aqueous solution, for example: HA (aq) - H+(aq) + A-(aq) The equilibrium constant will thus be given as products over reactants by: Ka is most commonly known as the 'acid dissociation constant'. The pKa is just the pH of the Ka i.e. pKa = -logKa and is used as a quantitative measure the strength of a weak acid in solution. Acetic acid (CH3COOH) is a weak acid and Sodium Hydroxide (NaOH), on the other hand, is a strong base and reacts with Acetic acid (CH3COOH) to produce water (H2O) and a salt (NaCH3OO) as follows: CH3COOH + NaOH --> H2O + NaCH3OO A method called a 'Titration' provides information about the behavior of acids through the pH scale. In a titration, base is gradually added until the acid reaches an endpoint or equivalence point. When the equivalence point is reached, the pH of the solution will change rapidly, because all the acid has reacted with the added base. A pH meter can be used to determine the pH of the