Determination of a Rate Equation
Determination of a Rate Equation Introduction: The rate of reaction is the rate of depletion of reactants or the formation of a product during a chemical reaction. It is expressed by units of concentration over the time taken for the reaction to take place. (Avogrados, 2010) Aim: To plan and carry out an experiment involving a graphical method to determine how the concentration of each component affect the rate of reaction in this reaction: 2HCl + Na2S2O3 --> 2NaCl + SO2 + S + H2O Background Information: Sodium thiosulphate and hydrochloric acid are both clear colourless solutions. They react together according to this equation: 2HCl + Na2S2O3 --> 2NaCl + SO2 + S + H2O When these solutions are mixed together, a yellow precipitate, sulphur, is produced. This causes the mixture to appear cloudy. The faster the rate of the reaction, the faster the solution appears cloudy. There are four basic factors that affect the rate of a reaction namely: Temperature, concentration/ pressure (in gases), physical state/ surface area of the reactants and the presence or absence of a catalyst [(Think Quest, 2008) and (WebChem, 2005)] Basic Idea: * Two sets of experiments will be carried out. In each case, the concentration for a single reactant will be varied * All other factors should remain constant * Conical flask containing the mixed reactants will be placed on a paper
Analysis of sulphur dioxide content in wine.doc
Analysis of sulphur dioxide content in wine Objective To determine the amount of sulphur dioxide, an antioxidant, present in wine by using volumetric analysis. Principle All free SO2 molecules is first convert into SO32- by NaOH solution: SO2 + 2OH- › SO32- + H2O Acidification of the solution liberates all SO2: 2SO32- + 2H+ › 2SO2 + 4H2O which is then titrated with 0.0057M iodine solution in which starch is used as end-point indicator: SO2 + I2 + 2H2O › 2HI + H2SO4 Chemicals white wine (carbonated), 1M NaOH, 2M H2SO4, 0.0057M I2, starch solution Apparatus volumetric apparatus, pipette, measuring cylinder, dropper, white tile Procedure 1.> Find out the volume of wine from the label on the bottle. 2.> Pipette 25cm3 of white wine into a conical flask. 3.> Add about 12cm3 of 1M NaOH and stand for about 15 minutes. 4.> Add about 10cm3 of 2M H2SO4 to the mixture and then few drops of starch solution as indicator. Quickly, titrate the mixture with 0.0057M iodine solution. 5.> Record the titre required to produce pale blue colour. 6.> Repeat steps 2-5 for 2-3 times. Data Analysis Trial st 2nd Final reading /cm3 3.05 2.80 26.30 Initial reading /cm3 0.25 9.70 23.25 Volume of I2 added /cm3 2.80 3.10 3.05 Average volume of I2 added /cm3 3.075 Concentration of I2 solution: 0.0057 M
Finding the number of Moles of Magnesium and Oxygen in Magnesium Oxide
Finding the number of Moles of Magnesium and Oxygen in Magnesium Oxide Table of Results: SUBSTANCE MASS/g Before After Crucible + lid 39.48 39.48 Crucible + lid + Magnesium 39.61 N/A Magnesium 0.13 N/A Crucible + lid + Magnesium Oxide N/A 39.63 Magnesium Oxide N/A 0.15 Oxygen N/A 0.02 Calculations for Empirical Formula: . Number of moles of Magnesium in Magnesium oxide: Moles/mol = Mass/g ____ Relative atomic mass/ g/mol Moles/mol = __ 0.13g__ = 0.00541 moles ( 3sf) 24g/mol 2. Number of moles of Oxygen in Magnesium oxide: Moles/mol = ____Mass/g______ Relative atomic mass/ g/mol Moles/mol = ___0.02g__ = 0.00125 moles ( 3sf) 16 g/mol 3. Put into ratio: Mg : O 0.00541 : 0.00125 0.00541 = 4.33 0.00125 4.33 : 1 12.99 : 3 13 : 3 Empirical Formula of Magnesium Oxide = Mg O Comparison between calculated empirical formula and literature empirical formula and Sources of Error: The literature empirical formula for Magnesium oxide is MgO meaning the ratio between Magnesium and Oxygen is 1:1. However the results from my experiment differed greatly. Our results ended up in a ratio of 13:3. This could be a result of numerous sources of error and the limitations of the method.
Investigation of Some of the Properties of a Pair of Cis-Trans Isomers
Experiment18 Aim To determination the partition coefficient of ethanoic acid between water and butan-2-ol. Procedure . The room temperature was recorded. 2. 15cm3 of the given aqueous ethanoic acid and 15cm3 of butan-2-ol were poured into a 100cm3 separating funnel, using suitable apparatus. The funnel was stoppered and was shook vigorously for 1 to 2 minutes. (The pressure in the funnel was released by occasionally opening the tap.) 3. 10cm3 of each layer was separated approximately. (The fraction near the junction of the two layers was discarded.) 4. 10.0cm3 of the aqueous layer was pipetted into a conical flask and was titrated with 0.1 M sodium hydroxide solution using phenolphthalein. 5. Using another pipette, 10.0 cm3 of the alcohol layer was delivered into a conical flask and was titrated with 0.1 M sodium hydroxide solution. 6. Steps (2) to (5) was repeated with another separating funnel using the following volume: 25cm3 of aqueous ethanoic acid and 15cm3 of butan-2-ol 7. For each experiment, the ratio of the concentration of ethanoic acid in the aqueous layer to that in the butan-2-ol layer was calculated. Result Room temperature: 29? Volume of butan-2-ol: 15 cm3 Volume of 0.2M ethanoic acid / cm3 Volume of 0.1M NaOH titre for aqueous layer / cm3 Volume of 0.1M NaOH titre for alcohol layer / cm3 Partition coefficient K= 5 0.00 2.55 0.796 25
Preparation of a Haloalkane
Experiment 2 Preparation of a Haloalkane Date: 11-9-2006 Objective To produce 2-chloro-2-methylpropane from 2-methylpropan-2-ol. To find the yield of 2-chloro-2-methylpropane. Introduction 2-chloro-2-methylpropane is formed when 2-methylpropan-2-ol and concentrated hydrochloric acid are added together. Because alcohols undergo substitution rapidly, the reaction takes place at room temperature. Afterwards, the haloalkane would be separated with a separating funnel, dried with anhydrous sodium sulphate and extracted by distillation. Procedure . About 9 ml of 2-methylpropan-2-ol was poured into a measuring cylinder and the measuring cylinder was weighed. 2. The 2-methylpropan-2-ol was poured into a 50ml separating funnel. The mass of the empty measuring cylinder was weighed again. 3. About 20ml of concentrated hydrochloric acid was added into the separating funnel, 3ml at a time. This procedure was carried out by the window side. 4. After each addition, the funnel was sealed and was shaken. The tap was opened at intervals to allow the gas produced to be released. 5. The separating funnel was allowed to stand near the window for 20 minutes. 6. A distillation apparatus was set up, as in the diagram below. 7. The small flask in the above set-up was weighed. 8. The lower aqueous layer in the separating funnel was discarded into a beaker. 9. Excess
Investigate the Properties of Ionic and Covalent substances
Title: To Investigate the Properties of Ionic and Covalent substances Introduction: Certain properties of compounds, such as polar and non- polar solvents, melting point and conductivity of electricity, can be used to distinguish between Ionic and Covalent substances. Aim: To determine whether common laboratory substances are ionic or covalent in nature. Apparatus/Materials: Sodium Chloride Test Tubes Sucrose Glass Rods Naphthalene Beaker (2- 100cm3) Copper (II) Sulfate Battery Calcium Carbonate Connecting wires Calcium Oxide Electrodes Spatulas Bunsen burner Tongs Method(1): Heating Substances Approximately two spatulas of sodium chloride was placed into a test tube and its contents were gently heated at first then heated strongly until no further change occurred. This was repeated with the other salts. Method(2): Solubility of Substances Two spatulas fall of sodium chloride was poured into breakers 1 with water and oe with ethanol. Solution was mixed and was held for conductivity test same was done for other salts. Method(3): Conductivity Electrodes were connected to connecting wires and
Green Chemistry - greenhouse gases and the ozone layer
The 'Greenhouse effect' ? The greenhouse effect keeps us warm ? But, the enhanced greenhouse effect is responsible for global warming. Infrared radiation comes into the atmosphere and gets absorbed by the C=O, O-H and C-H bonds in H2O, CH4 and CO2. They vibrate gaining EK, which is dispersed, warming the Earth's surface. The greenhouse effect of a given gas is dependent on the: ? Concentration in the atmosphere (High CO2 etc) ? The ability to absorb infrared radiation (i.e. the bonding in it) The IPCC (bunch of chemists) collects evidence to force governments to stop producing so much CO2. Scientists should research ways in which global warming can be reduced ? Carbon-Capture and Storage (CCS)- This involves converting CO2 into liquid form. This liquid can be injected deep underground. ? Also reaction with metal oxides to form carbonates. (Magnesium Oxide) MO(s) + CO2(g) --> MCO3(s) ? The Kyoto Protocol was signed by developed nations governments to reduce output of greenhouse gasses to offset the progress of global warming. The scheme involved using carbon credits which can be traded around to penalise polluting nations. Some nations (Australia, USA (Obama)) are reluctant to join because of the impact on their economies.(See Geog notes) The ozone layer The Ozone Layer absorbs much of the harmful ultraviolet radiation emitted by
ACID RAIN The majority of people consider rain to be an undamaging weather occurrence. However the increase in acidity of rain is both unsafe and damaging. In order to fully understand the term acidity,
ACID RAIN The majority of people consider rain to be an undamaging weather occurrence. However the increase in acidity of rain is both unsafe and damaging. In order to fully understand the term acidity, it is essential to know something about the pH scale. This scale has a range of 0 to 14, with 7 being neutral. Anything below 7 (0-6) is known to be acidic and anything above 7 (8-14) is alkaline. A change in only one unit is equal to a tenfold increase in the strength of the acid or base. Therefore a unit change from pH 6 to pH4 is equal to a 10 x 10 increase in it acidity. Taking the above into consideration, it is easy to see how the normal phenomenon "rain" is becoming more and more acidic as its pH has dropped from around 6and 7 to about 4.3and 5.3.This occurrence is known as Acid Rain and was first noted in1852 by the English chemist called Robert Angus Smith. Acid rain in other words is the term used to describe rainfall that has a pH level below5.6. It is a form of air pollution that is currently a theme of huge debate due to its wide spread damages. It is responsible for the destruction of thousands of lakes and streams in the United States, Canada and parts of Europe. Acid Rain formation The two most important primary sources of acid rain are sulphur dioxide (SO2) and oxides of nitrogen (NOx). Sulphur is a colourless, pungent gas produce during the
Chemical Bonding and CFCs. There are three main types of chemical bonds.
Introduction: Chemical bonds are formed as a result of rearrangement of electrons between atoms with the effect of lower the energy of the system as a whole. The chemical bond is a binding force to hold atoms together to form an aggregate with sufficient stability for the chemists to consider the aggregate an independent species. There are three main types of chemical bonds. Types of Bonds Ionic bond These are formed as a result of electron transfer between an electropositive element and an electronegative element to form cations and anions. The electrostatic attraction between cations and anions form the ionic bond. E.g., NaCl. Covalent bond These are formed as a result of sharing of electrons between two electronegative atoms. Both atomic nuclei attract the shared electrons which are mainly located at the mid-point between the two bonding nuclei, resulting in a net attractive force between the two nuclei. This electrostatic force holding the atoms together forms the covalent bond. This accounts for the formation of molecules in elements (e.g., H2) and for formation of molecular compounds (e.g., CCl4). Metallic bond Electropositive elements(e.g., Na) can share their outermost shell electrons in the form of a 'sea of electrons', while the remaining part of the atoms are arranged regularly in a giant lattice of cations. The electrostatic attraction of the
Scientists and Theories of Atomic Structure
Maryam Khan Scientists and atomic structure The structure of an atom has taken many years to develop as what we now know it to be. It consists of the hard work of many scientists, their developments and theories. Since 400BC from when the atom model was just a ball to 1913 when it became the bohr model and the atom which we now know it to be. The first of many people who played a role in this vital development of the atomic structure is the Greek philosopher Democritus with his theory of the ‘atomos’ meaning ‘not to be cut’. Democritus was quite ahead of his time with this study and discovery. He began his research for a description of matter - Could it divided forever or is there a limit to how many times it can be divided. He later concluded that the atom was like a billiard ball that couldn’t be split any further and this is what you would end up with if you divided a sample of matter so many times and therefore was ‘indivisible’. His theory stated that atoms were small, hard particles all made up of the same material however they were different shapes and sizes. He also said that these indivisible pieces (atoms) were infinite – always moving and capable of moving together. However his theory was not widely accepted and forgotten about for over the next 2000 years. Later in the early 1800s an English chemist named John Dalton performed experiments which
