...Laboratory Exercise Two Reaction Enthalpies for Acid – Base Neutralization Reactions Goals 1. To measure the amount of heat released in acid-base neutralization reactions. 2. To determine the molar enthalpy change for each acid-base neutralization reaction. 3. To validate Hess’s Law using the experimental results. Background Information Acids and bases react together to produce a salt and water as shown in the following reaction. HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) This type of reaction is called a neutralization reaction. When a neutralization reaction occurs, heat (q) is released to the surroundings, and the temperature of the surroundings rises. In aqueous acid-base neutralization reactions the surroundings are the solution itself, which is mainly composed of water. The amount of heat released by the reaction can be determined by measuring the temperature change of the solution during the reaction. At constant pressure, the heat released by a reaction is the reaction enthalpy (∆Hr). The units for reaction enthalpies are kJ mol-1; in reactions that don’t have a 1-to-1 ratio of all reactants and products, we need to specify per mol of which species. In this experiment, the heat released by each reaction will be used to determine the reaction enthalpy for each chemical reaction per mole of acid reacted. (Note that this may or may not be the same thing as “per mole of acid added;” you will need to think about limiting reagents.) During the experiments the temperature change...
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...ID: 1404405 Title of Experiment: Determination of The Enthalpy (Heat) of Reaction of A Monobasic Acid with Sodium Hydroxide No. of Experiment: 12 Date of Experiment: 2/2/2016 Date of Submission: 24/2/2016 Group members: 1)Chong Chi Wei 2)Mong Lai Wan 3)Ang Yen Yuan Name of Lecture: Dr. Sim Yoke Leng Title: Determination of the Enthalpy (Heat) of Reaction of A Monobasic Acid with Sodium Hydroxide Objective: 1. To understand the enthalpy chemistry. 2. To determine the calorimeter constant. 3.To determine the enthalpy of reaction of acid-base reactions. Introduction: Heat is associated with nearly all chemical reactions. In such instances, the reaction either liberates heat (exothermic) or absorbs heat (endothermic). When a reaction is carried out under constant pressure (as in an open beaker) the heat associated with the reaction is known as enthalpy. The symbol for enthalpy is ΔH. It is most often too difficult to direct measure the enthalpy change for a reaction. What can be done is to measure the heat changes that occur in the surrounding by monitoring temperature changes. Conducting a reaction between two substances in aqueous solution, allows the enthalpy of the reaction to be indirectly calculated with the following equation. q=m x c x Δ t The term q represents the heat energy that is gained or lost. C is the specific heat of water, m is the mass of the water and Δ t is the temperature change of the reaction mixture. The specific...
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...Introduction: Often times when we think of acids and bases we recognize acids and bases by their simple properties, such as taste. We know that a lemon is sour, so it is acidic. Bases tend to taste bitter. However, when working in laboratory chemists cannot rely on their taste buds to predict the result of the many reactions they encounter. It is important to know the classification and the formula of acids and bases in order to understand how one substance will react with another. In this lab we observed how acids and bases change the color of certain dyes, such as litmus. We also observe the solubility of certain salt compounds. When solids dissolve in water, they dissociate to give the elementary particles from which they are formed. As a result, ionic solids dissociate to give solutions of the positive and negative ions they contain. Experiment Please refer to Report Sheet Calculations Please refer to Report Sheet for pH values of acid bases and salts utilized in the lab experiment Reaction of Salt mixtures FeCl3 + CoCl2 ( FeCl2 + CoCl3 Complete: Fe3+ + 3Cl- + Co2+ + 2Cl- ( Fe2+ + 2Cl- + Co3+ + 3Cl- Net: Fe3+ + Co2+(Fe2+ + Co3+ CoCl2 + Na2CO3 ( CoCO3 + Na2Cl2 Complete: Co2+ + 2Cl- + 2Na+ + (CO3)2- ( CoCO3 + 2NA+ + 2CL- Net: Co2+ + CO3 2- ( CoCO3 CuSO4 + Na2CO3 ( CuCO3 + Na2SO4 ionic: Cu+2 + SO4-2 + Na2+1 + CO3-2 ( CuCO3 + Na2+1 + SO4-2 Net: CO3- + Cu+ ( CuCO3 CuSO4 + Na3PO4 ( Cu3(PO4)2+Na2SO4 Complete:Cu+2 + SO4-2 + 6Na+ PO4(3-)+2...
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...Pg(303-309/312-314) 3/11/14 Experiment #36 and 36b Preparation of the Grignard Reagent and Benzoic Acid Purpose- In this experiment we learned to prepare a Grignard reagent, phenyl magnesium bromide, which we then converted to a carboxylic acid. Procedure & Observations- First we started by setting up our apparatus for Grignard reactions. We started by making sure all glassware was completely dried as a Grignard reaction would not occur if water is present. We used a 100ml round bottom flask for our solution and placed it on a hot plate to control the heating process. We then weighed out 0.4920g of magnesium turnings and placed it into the round bottom flask. We also measured out 2.1ml of bromobenzene into a 50ml flask and got a weight of 3.0557g. We then added 10ml of ether to the 2.1ml of bromobenzene and pipetted half into the round bottom flask. The other half was then added to the separatory funnel along with an additional 7ml of ether. From here we began heating the mixture until boiling started to occur. Once the reaction started to begin we got an instant brownish color change. We also ended up using a drop from another group’s reaction to help move along the process. Once this happened we began slowly adding the remaining bromobenzene over a five minute period. Once it had all been added we added an additional 1ml of ether to rinse the funnel. We then heated under gentle reflux till all the magnesium...
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...Module 9 : Experiments in Chemistry Lecture 38 : Titrations : Acid-Base, Redox and Complexometric Objectives In this lecture you will learn the techniques to do following Determination of the amount of sodium carbonate and sodium hydroxide in a mixture by titration. Carrying out acid-base titration using a pH meter. Carrying out acid-base titration by conductometric measurement. Determination of the composition of a mixture of acetic acid and hydrochloric acid by conductometric titration. Determination of ferrous ion using potassium dichromate by internal indicator. Determination of hardness (Ca2+ ) of water using EDTA – complexometry method. In this lecture, you will be introduced to a few experiments in chemistry. These experiments complement the theory you have learned in chemical equilibrium and kinetics. 38.1 Acid-Base Titrations: Acid-base reactions are of great practical importance in analysis, not only because of their use in titrating a large number of inorganic and organic substances, but also because the hydrogen ion concentration of a solution often is of great importance in controlling reactions. Titration : The process of determining the volume of a given solution of a reagent equivalent to the amount of another reactant present in a standard solution is known as titration. Equivalent Weight of Acids and Bases : The equivalent weight of an acid is that weight which yields one mole of hydrogen ions in the reaction employed whereas the equivalent weight of...
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...uk/doc/open-government-licence/ or e-mail: psi@nationalarchives.gsi.gov.uk. Where we have identified any third party copyright information you will need to obtain permission from the copyright holders concerned. Any enquiries regarding this document/publication should be sent to us at enquiries@educationscotland.gov.uk. This document is also available from our website at www.educationscotland.gov.uk. Contents Introduction 5 Chemical analysis 6 Qualitative and quantitative analysis 6 Volumetric analysis 6 Gravimetric analysis 14 Colorimetric analysis 17 Organic techniques 22 Introduction 22 Preparation 22 Isolation 24 Purification 29 Identification 33 Percentage yield 37 Errors 39 Accuracy and precision 39 Repeatability and reproducibility 41 Quantifying errors 41 Absolute uncertainties and percentage uncertainties 42 Combining uncertainties 43 Some ‘forgotten’ uncertainties 46 Experiments 53 Experiment 1A: Preparation of a standard solution of 0.1 mol l–1 oxalic acid 53 Experiment 1B: Standardisation...
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...POINT LISAS CAMPUS Esperanza Road, Brechin Castle, Couva www.utt.edu.tt LAB 1 Decomposition reaction Aim: Determination of the number of moles of water molecules of crystallization present in hydrated Magnesium Sulphate (MgSO4.xH2O) Apparatus: Mass balance, test tube, test tube holder, heat-proof mat and bunsen burner. Reagents: Hydrated sodium carbonate. Theory: Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simple compounds. A more specific type of decomposition is thermal decomposition or thermolysis, which is caused by heat. ABA+B, the reaction is endothermic, since heat is required to break the chemical bonds. Most decomposition reaction require energy either in the form of heat, light or electricity. Absorption of energy causes the breaking of the bonds present in the reacting substance which decomposes to give the product. When a hydrated salt is heated it decomposes into a pure form of the salt and water. MgSO4.xH2O MgSO4 + H2O Procedure: Refer to Handout Results: A. Mass of test tube/g = 21.77 B. Mass of the tube and salt/g = 24.0 A table showing the mass of the test tube and salt after 3 consecutive heating: Heating | Mass of the test tube and salt/g | 1st | 23.96 | 2nd | 23.81 | 3rd | 23.81 | Calculations: G. Mass of anhydrous magnesium sulphate/g = F - A = 23.81 – 21.77= 2.04 H. Mass of water of crystallization evaporated/g...
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...Chemistry 1B Experiment 16 77 16 Qualitative Analysis Introduction The purpose of qualitative analysis is to determine what substances are present in detectable amounts in a sample. This experiment has two parts. In the first part, you will analyze an unknown solution for the presence of seven common ions. In the second part, you will test an unknown solid to determine which of two possible identities is correct. Part I. Spot Tests for Some Common Ions A simple approach to the qualitative analysis of an unknown solution is to test for the presence of each possible ion by adding a reagent which will cause the ion, if it is in the sample, to react in a characteristic way. This method involves a series of “spot” tests, one for each ion, carried out on separate samples of the unknown solution. The difficulty with this way of doing qualitative analysis is that frequently, particularly in complex mixtures, one species may interfere with the analytical test for another. Although interferences are common, there are many ions which can be identified in mixtures by simple spot tests. In this experiment we will use spot tests for the analysis of a mixture which may contain the following commonly encountered ions in solution: CO32– SO42– PO43– SCN Cl – – carbonate sulfate phosphate thiocyanate chloride acetate ammonium C2H3O2– NH4+ 78 Chemistry 1B Experiment 16 The procedures we involve simple acid-base, precipitation, complex ion formation or oxidation-reduction...
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...by volume. c) Air bubbles in the substance would cause the volume to be wrong therefore affecting the density. 2. An experiment that you can determine what large supply of unlabeled indicator paper is to put drops of different solutions on the paper and observe if a chemical reaction takes place. By taking a stirring rod and placing a drop of hydrochloric acid on to each paper and record if a color change takes place. The repeat is the process with water and sodium hydroxide solution. Depending if the paper has no change at all or if it turns pink or blue will let you know if an acid, base, or neutral solution was placed on the paper. 3. A simple experiment would allow you to determine which bottle contains what solution is placing a few drops of each on litmus paper. The hydrochloric acid will turn the blue paper red because it is an acidic solution. The sodium chloride solution will not show any change on the paper because it is a neutral solution. Finally, the sodium hydroxide will turn the red litmus paper blue because it is a basic solution. 4. An experiment that would allow me to determine which bottles contains solid sodium chloride or solid sodium carbonate would be to add hydrochloric acid to each and observe the reactions to see if carbon dioxide would form. The sodium carbonate would bubble. 5. The chemical reaction for heating of malachite is Cu(OH)2 CO3 + heat= CuO+H2O. The...
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...Acis CHEMICAL REACTIONS: ACID-BASE BUFFERS Short Overview Acids and bases represent two of the most common classes of compounds. Many studies have been done on these compounds, and their reactions are very important. Perhaps the most important reaction is the one in which an acid and base are combined, resulting in the formation of water (in aqueous solution) and a salt; this reaction is called neutralization. A buffer solution is a solution that contains both an acid and a salt containing the conjugate base anion in sufficient concentrations so as to maintain a relatively constant pH when either acid or base is added. In this experiment you will prepare a buffer solution and observe its behavior when mixed both with an acid and a base. You will also compare the behavior with that of solutions containing only the acid. Theory In his theory of ionization in the 1880’s, Svante Arrhenius defined acids are substances which form H+ and bases as substances which form OH- in water. He further defined a salt as a substance other than an acid or base which forms ions in aqueous solution. Such substances are thus capable of producing an electric current and are called electrolytes. The amount of electricity produced is directly proportional to the concentration of ions in solution. With regard to electrolytes we have learned previously that strong acids and strong bases ionize completely, and are therefore strong electrolytes because they...
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...185 EQUILIBRIUM 185 UNIT 7 EQUILIBRIUM After studying this unit you will be able to • identify dynamic nature of equilibrium involved in physical and chemical processes; • state the law of equilibrium; • explain characteristics of equilibria involved in physical and chemical processes; • write expressions for equilibrium constants; • establish a relationship between Kp and K c ; • explain various factors that affect the equilibrium state of a reaction; • classify substances as acids or bases according to Arrhenius, Bronsted-Lowry and Lewis concepts; • classify acids and bases as weak or strong in terms of their ionization constants; • explain the dependence of degree of ionization on concentration of the electrolyte and that of the common ion; • describe pH scale for representing hydrogen ion concentration; • explain ionisation of water and its duel role as acid and base; • describe ionic product (Kw ) and pKw for water; • appreciate use of buffer solutions; • calculate solubility product constant. Chemical equilibria are important in numerous biological and environmental processes. For example, equilibria involving O2 molecules and the protein hemoglobin play a crucial role in the transport and delivery of O2 from our lungs to our muscles. Similar equilibria involving CO molecules and hemoglobin account for the toxicity of CO. When a liquid evaporates in a closed container, molecules with relatively higher kinetic energy escape the liquid surface into the vapour...
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...work. It also will give information on the role of substrates and how it affects enzymes. In the first experiment, we examined whether or not the speed of the reaction will be influenced positively by an increase of heat to a point where it will not be denatured, but negatively by a decrease of heat. In the second experiment we looked to see if the speed is influenced positively by an increase of enzymes to a point, but negatively affected by a decrease of enzymes. For the third experiment the hypothesis was to see if the speed of the reaction is influenced by the amount of substrate in the environment. There is another test conducted to see if the enzyme will not be able...
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...Introduction The first experiment today will be the titration of acetic acid in vinegar. Vinegar is a solution of acetic acid, an organic acid of formula CH3COOH (MW = 60.0526 g/mole). In order to be sold as vinegar, it needs to meet the FDA’s guideline of 5.00% acetic acid by mass. Knowing that the density of vinegar is 1.04 g/mL and analyzing this solution by titration, chemists can determine the mass percentage of acetic acid in a sample of vinegar. The titration reaction is given below: CH3COOH + NaOH ( CH3COONa + H2O Reaction 1 A customer has purchased a vinegar solution at a local thrift store at a 20% discount and he believes that the sample of vinegar he has purchased does not meet FDA regulations. He is suing the thrift store for the $0.36 he feels that he has been cheated out of. The court has asked you to analyze the sample and render your verdict. Does this sample conform to the FDA guideline? If 2.00 mL of the thrift store vinegar required 9.73 mL of 0.150 M NaOH to reach the endpoint, then 0.00877 g of acetic acid was present. 9.73 mL NaOH x 1 liter NaOH x 0.150 mole NaOH x 1 mole CH3COOH x 60.0526 g CH3COOH 1000 mL 1 liter 1 moles NaOH 1 mole CH3COOH = 0.0876 grams CH3COOH in sample 2.00 mL vinegar x 1.04 g vinegar = 2.08 g vinegar 1 mL 0.0876 g CH3COOH x 100 = 4.21 % CH3COOH by mass 2.08 g vinegar sample You can find the molarity of acetic acid in vinegar by dividing...
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...Experiment : Title : Objective : 1 Preparation of standard solution and standardization of hydrochloric acid To prepare a standard solution of sodium carbonate and use it to standardize a given solution of dilute hydrochloric acid. Anhydrous sodium carbonate is a suitable chemical for preparing a standard solution (as a primary standard). The molarity of the given hydrochloric acid can be found by titrating it against the standard sodium carbonate solution prepared. The equation for the complete neutralization of sodium carbonate with dilute hydrochloric acid is Na2CO3(aq) + 2HCl(aq) → 2NaCl(aq) + CO2(g) + H2O(l) The end-point is marked by using methyl orange as indicator. Introduction : Chemicals : Apparatus : Procedure : solid sodium carbonate, 0.1 M hydrochloric acid 1. 2. 3. 4. 5. 6. 7. 8. Weight out about 1.3 g of anhydrous sodium carbonate accurately using the method of “weighing by difference”. Transfer the weighed carbonate to a beaker and add about 100 cm3 of distilled water to dissolve it completely. After dissolving, transfer the solution to a 250.00 cm3 volumetric flask. Rinse the beaker thoroughly and transfer all the washes into the volumetric flask. Remember not to overshoot the graduation mark of the flask. Make up the solution to the mark on the neck by adding water. Pipette 25.00 cm3 of sodium carbonate solution to a clean conical flask. Add 2 drops of methyl orange indicator to the carbonate solution. Titrate the carbonate solution with the...
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... AA Acids, Bases & Indicators Comprehensive tutorial notes Julius G.Thungu jgthungu@gmail.com 0711 354 885 INTRODUCTION TO ACIDS, BASES AND INDICATORS 1.In a school laboratory: (i)An acid may be defined as a substance that turn litmus red. (ii)A base may be defined as a substance that turn litmus blue. Litmus is a lichen found mainly in West Africa. It changes its colour depending on whether the solution it is in, is basic/alkaline or acidic. It is thus able to identify/show whether another substance is an acid, base or neutral. (iii)An indicator is a substance that shows whether another substance is a base/alkaline,acid or neutral. 2.Common naturally occurring acids include: Name of acid | Occurrence | 1.Citric acid | Found in ripe citrus fruits like passion fruit/oranges/lemon | 2.Tartaric acid | Found in grapes/baking powder/health salts | 3.Lactic acid | Found in sour milk | 4.Ethanoic acid | Found in vinegar | 5.Methanoic acid | Present in ants, bees stings | 6.Carbonic acid | Used in preservation of fizzy drinks like coke, Lemonade, Fanta | 7.Butanoic acid | Present in cheese | 8.Tannic acid | Present in tea | 3.Most commonly used acids found in a school laboratory are not naturally occurring. They are manufactured. They are called mineral acids. Common mineral acids include: Name of mineral acid | Common use | Hydrochloric acid (HCl)...
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