...Purpose How do we determine the reaction type and write a balanced equation for chemical reactions? Background Discussion There are many kinds of chemical reactions and several ways of classifying them. One popular and useful method is to classify reactions into five major types. These are: (1) synthesis, (2) decomposition, (3) single replacement, (4) double replacement, and (5) combustion. Most reactions can be put into one of these categories. In a synthesis reaction, two or more substances (elements or compounds) combine to form a more complex substance. A decomposition reaction is exactly the opposite of a synthesis reaction. In a decomposition reaction, a compound breaks down into two or more simpler substances (elements or simpler compounds.) In a single replacement reaction, one element in a compound is replaced by a more active element. In a double replacement reaction, the positive ions of two different ionic compounds can be thought of as “replacing each other.” Most replacement reactions (both single and double) take place in aqueous solutions containing free ions. In a double replacement reaction, one of the products must be removed from the solution as a precipitate, water, or an insoluble gas. A precipitate is a solid that is produced as a result of a chemical reaction in solution. As the precipitate separates from the solution, the solution appears cloudy. In a combustion reaction a substance combines with oxygen, releasing a large amount...
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...Measurement of Fe2+ in Iron Pills Redox Titration Purpose: You will prepare and standardize a potassium permanganate solution and use it to determine the amount of iron, specifically Fe2+, in iron pills. Overview: Titration is the volumetric measurement of a solution of known concentration when it reacts completely with a measured volume or mass of another substance. In the first part of this experiment, the potassium permanganate solution, the titrant, is standardized, by quantitatively reacting it with iron (II) ammonium sulfate hexahydrate, Fe(NH4)2(SO4)2•6H2O (abbreviated FAS). The second part of the lab uses the standardized potassium permanganate to determine the amount of the analyte, also iron (II), in iron supplement pills. In this experiment, a purple-colored solution of potassium permanganate, KMnO4, with an approximate concentration of 0.02 M will be added to solutions containing Fe2+ ions. In redox titration the chemical reaction is an oxidation-reduction reaction with electrons transferred from one species to another. The total number of electrons lost in the oxidation half-reaction is equal to the total number of electrons gained in the reduction half-reaction. The permanganate ion, MnO4-, is a strong oxidizing agent which causes the Fe2+ to be oxidized to Fe3+ ions. The manganese gains five electrons and is reduced from a 7+ oxidation state in the permanganate ion to form colorless Mn2+ ions. The Fe2+ loses one electron as it is oxidized to Fe3+...
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... dropper, 4 pieces of magnesium ribbon, 4 pieces of zinc metal, 4 pieces of copper wire, copper (II) sulfate solution, zinc nitrate solution, magnesium nitrate solution, sodium carbonate solution and hydrochloric acid. Procedure: Part A: Single Displacement Reactions 1. Clean 4 pieces of magnesium ribbon, zinc metal and copper wire with steel wool until they are shiny. 2. Half-fill one column (three wells) of the well plate with the copper (II) sulfate solution. 3. Half-fill a second column (three wells) with the zinc nitrate solution. 4. Half-fill a third column (three wells) with the hydrochloric acid. 5. In each column, place 1 piece of each metal in different wells (Magnesium in one well, zinc in another and copper in the last). Use a toothpick to keep the metals submerged in the solution. 6. Observe the different reactions in each well. Record your observations in a table. 7. Save the contents of the wells for Part B. Part B: Double Displacement Reactions 1. Add 3 drops of the sodium carbonate solution to each of the wells from Part A. 2. Record your observations in a table. 3. Dispose of the contents of the well plate as directed by your teacher. Clean your workstation and wash your hands. Observations: Reactants | Physical Properties | Results | Physical/Chemical Changes | Copper (II) sulfate | Blue, clear, liquid | N/A | N/A |...
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...physical and chemical properties of gases and to be able to use these properties to identify these gases. PROCEDURE To start I diluted 6M HCl by pouring 6ml of distilled water in a graduated cylinder. I added drop by drop 3ml of HCl directly from the bottle. The mixture was mixed well and the diluted 9ml solution was added to the test tube. Hydrogen: I placed a place of Zn metal in the test tube with the diluted solution. I then capped the test tube with a rubber stopper with a short, straight plastic gas delivery tube through the center. The test tube was then placed into one of the wells on the well plate. The test tube had to be upright so it was necessary to wrap the tube with a piece of paper towel to hold it into place. Reaction was observed and recorded. A pipette bulb was filled with water and placed on top of the test tube’s gas delivery tube. The well plate with the test tube was placed in the tin while the gas displaced some of the water. When the water in the pipette was completely replaced by the gas I quickly removed it and placed my finger over the opening to prevent any gas from escaping. I lit a match and gently squeezed out some of the gas and observed and recorded the reaction. I then took a marker and marked 3 equal parts on the pipette. The pipette was again filled with water and placed on the gas generation tube like previously. When the bulb was 2/3 filled with gas it was removed and placed in a well with the opening done to be used later...
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...Experiment 8: Redox: Analysis of the Oxidizing Capacity of Bleach PURPOSE In this experiment, you will show how redox reactions can be used to quantitatively determine the amount of oxidizing agent in liquid hypochlorite household bleach. There are two oxidation-reduction reactions for determining the oxidizing capacity of bleach. Initially an excess of iodide ions are added to a bleach solution. The iodide ions are oxidized to iodine after the solution has been acidified. Starch is added to the resulting iodine solution as an indicator. The solution is then titrated with sodium thiosulfate until the color of the solution changes indicating the endpoint of the reaction. Data collected from the titrations will be used to calculate the mass of the sodium hypochlorite in an unknown solution of bleach. Given the original mass of the unknown solution and the calculated mass of the sodium hypochlorite in the unknown solution, the percent by mass of the sodium hypochlorite can be determined. The oxidizing capacity of the unknown bleach is effectively the percent by mass of the sodium hypochlorite in the unknown bleach sample. OJECTIVES 1) Titration of a sample of bleach with thiosulfate. 2) Determining the end point of the titration with starch indicator. 3) To determine oxidizing capacity of bleach by determining the percentage by mass of the bleach that is sodium hypochlorite. 4) Balance and summarize the two redox reactions to determine the overall chemical reaction that...
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...Determining the Limiting Reactant and Percent Yield in a Precipitation Reaction Objectives: • Observe the reaction between solutions of sodium carbonate and calcium chloride. • Determine which of the reactants is the limiting reactant and which is the excess reactant. • Determine the theoretical mass of precipitate that should form. • Compare the actual mass with the theoretical mass of precipitate and calculate the percent yield. Materials: Balance 0.70 M sodium carbonate solution, Na2CO3(aq) Graduated cylinder 0.50 M calcium chloride solution, CaCl2(aq) Beaker (250 mL) Wash Bottle (distilled H2O) Filter paper Funnel Iron ring Ring stand Procedure: Part I: The Precipitation Reaction (Day 1) 1. Obtain two clean, dry 25 mL graduated cylinders and one 250 mL beaker. 2. In one of the graduated cylinders, measure 25 mL of the Na2CO3 solution. In the other graduated cylinder, measure 25 mL of the CaCl2 solution. Record these volumes in your data table. 3. Pour the contents of both graduated cylinders into the 250 mL beaker and observe the results. Record these qualitative observations in your observations table. Allow the contents of the beaker to sit undisturbed for approximately 5 minutes to see what happens to the suspended solid particles. Meanwhile, proceed to step 4. 4. Obtain a piece of filter paper and put your initials and your partner’s initials on it using a pencil. Measure and record the mass of the filter paper, then use it to...
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...Lab: Investigating Photosynthesis and Cellular Respiration Background: All organisms are dependent on a healthy carbon dioxide-oxygen balance. Photosynthesis and cellular respiration are key processes in maintaining this balance. Plants, through the process of photosynthesis, use energy absorbed from sunlight, water, and carbon dioxide to produce sugars and oxygen. Animals and plants, through the process of cellular respiration, use oxygen and sugars to produce carbon dioxide, water, and the energy needed to maintain life. Purpose: To determine how carbon dioxide cycles through a biological system by performing the “Carbon Transfer Through Snails and Elodea” lab activity. Procedure: 1. Read through the background information and purpose. Create your own question for what you are investigating in this experiment. a. Problem (in question form): How are photosynthesis and cellular respiration related? 2. Obtain 8 test tubes of equal size/volume and number the test tubes 1-8. Fill each test tube with approximately 30 mL of deionized water. 3. Add enough bromothymol blue (BTB) indicator to solution to each test tube to change the water to a green color (about 3 mL). 4. What is Bromothymol Blue? Why is the BTB in the test tube green (Hint: recall the teacher demonstration)? Bromothymol blue is an indicator that changes color when carbon dioxide is present. Green in the test tube means a low carbon dioxide presence. 5. If snails use lungs...
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...unknown concentration. The more accurately the concentration of the solution of known concentration is known, the more accurately the concentration of the unknown solution can be determined. Some chemicals can be purchased in a pure form and remain pure over a long period or time. Other chemicals are easily contaminated by the absorption of carbon dioxide or water from the air. Sodium hydroxide absorbs moisture from the air and often appears wet. Thus if a solution of sodium hydroxide is prepared by weighing the sodium hydroxide, the concentration of the solution may not be precisely the intended concentration. Potassium hydrogen phthalate on the other hand, has a lesser tendency to absorb water from the air and when dried will remain dry for a reasonable period of time. Potassium hydrogen phthalate may be purchased in pure form at reasonable cost. Potassium hydrogen phthalate is a primary standard. This means that carefully prepared solutions of known concentration of potassium hydrogen phthalate may be used to determine, by titration, the concentration of another solution such as sodium hydroxide. The equation for the reaction of potassium hydrogen phthalate with sodium hydroxide is: KCO2C6H4CO2H + NaOH ( KCO2C6H4CO2Na + H2O The equivalence point of a titration occurs when chemically equivalent amounts of acid and base are present. At this point the pH changes rapidly with a small addition of acid or base. If a pH meter is used in the titration and the pH...
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...unknown concentration. The more accurately the concentration of the solution of known concentration is known, the more accurately the concentration of the unknown solution can be determined. Some chemicals can be purchased in a pure form and remain pure over a long period or time. Other chemicals are easily contaminated by the absorption of carbon dioxide or water from the air. Sodium hydroxide absorbs moisture from the air and often appears wet. Thus if a solution of sodium hydroxide is prepared by weighing the sodium hydroxide, the concentration of the solution may not be precisely the intended concentration. Potassium hydrogen phthalate on the other hand, has a lesser tendency to absorb water from the air and when dried will remain dry for a reasonable period of time. Potassium hydrogen phthalate may be purchased in pure form at reasonable cost. Potassium hydrogen phthalate is a primary standard. This means that carefully prepared solutions of known concentration of potassium hydrogen phthalate may be used to determine, by titration, the concentration of another solution such as sodium hydroxide. The equation for the reaction of potassium hydrogen phthalate with sodium hydroxide is: KCO2C6H4CO2H + NaOH ( KCO2C6H4CO2Na + H2O The equivalence point of a titration occurs when chemically equivalent amounts of acid and base are present. At this point the pH changes rapidly with a small addition of acid or base. If a pH meter is used in the titration and the pH...
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...Second Order Reaction Kinetics Abstract The objective of this experiment was to determine if the specific rate constant of the reduction reaction of hexacyanoferrate (III) ion with ascorbic acid (C6H8O6) is affected by the ionic strength of the solution and the charges of the ion species within the solution. A Cary Bio 50 Spectrophotometer and its associated software was used to measure the absorbance of the solution at a wavelength of 418 nm. Analysis of the data collected supports the conclusion that the ionic strength of the solution and the charges of ions on the activated complex have a direct relation to the rate constant. The experimental value of 2.237 for the ionic strength of 0.025 M when compared to the literature value of 1.72 in a similar experiment by Nobrega and Rocha, has a percent error of 30%. For the ionic strength of 0.05 M, the percent error between the experimental value 2.851 and the literature value of 2.58 was 11%. The ionic strength of 0.1 had an error of -1% between the literature value of 3.97 and the experimental value 3.924. For the ionic strength of 0.2 there was a -23% error between the experimental value of 5.301 and the literature value of 6.89 (Nobrega, 1997). The experimental value of the product of the charges of the ions in the activated complex, 2.1, was lower than the expected value 3, which could be due to the shielding of the charges on the reactants due to the ions witihin the solution. Introduction The reduction of the hexacyanoferrate...
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...NATIONAL QUALIFICATIONS CURRICULUM SUPPORT Chemistry A Practical Guide Support Materials [REVISED ADVANCED HIGHER] [pic] The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of all NQ support materials, whether published by Education Scotland or others, are reminded that it is their responsibility to check that the support materials correspond to the requirements of the current arrangements. Acknowledgement © Crown copyright 2012. You may re-use this information (excluding logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view this licence, visit http://www.nationalarchives.gov.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...
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...Jacob Alfaro BIOL 251 Whittier College Jacob Alfaro BIOL 251 Whittier College Effect of Ebony and Wild Type Phenotypes on the Natural Selection and Fitness of Drosophila November 2015 Effect of Ebony and Wild Type Phenotypes on the Natural Selection and Fitness of Drosophila November 2015 INTRODUCTION: There are many different Drosophila phenotypes. This experiment focuses on the ebony and wild type phenotypes. These phenotypes affect color. The ebony flies more dark and the wild type flies are much lighter. The ebony is recessive and therefore carries two copies of the recessive allele, therefore the Drosophila are homozygotes. But wild type is dominant, meaning that heterozygotes and homozygotes represent the wild type phenotype. A phenotype is a physical characteristic as a result of a genotype affected by its environment (Brooker et al, 2011). A genotype is the set of...
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...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 given dilute hydrochloric acid until the colour of solution just changes from yellow to orange. Repeat the titration two times. Calculation : Results : Questions : Calculate...
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...» April 22, 2011 — Ritual fasting has been part of religious traditions for thousands of years, from Muslims who fast during daylight hours in the month of Ramadan to Mormons who take a regular break from food the first Sunday of each month. But a recent growing body of research shows that abstaining from food intermittently may have physical as well as spiritual benefits — the latest, a study from Utah researchers that found that occasional fasts (defined as extended periods of time in which people generally abstain from all food and drink except for water) may reduce the risk of heart disease and diabetes. Google “fasting for health” and you’ll get more than 7 million hits, ranging from doctors who recommend it in their practices to treat a range of diseases, spas that promise detoxifying food-free vacations, and message board postings from devotees who say that fasting makes them feel clearer mentally and more fit. “I fast whenever my body feels like it needs a reboot,” says Yoli Ouiya, 31, a New York City blogger who writes about eco-friendly living. She fasts once every few months. But is fasting a good idea for your health? Possibly, says David Katz, MD, MPH, director of the Prevention Research Center at Yale University. Every day, organs such as the liver, kidney, and spleen work to remove and neutralize toxins from the body to keep our cells healthy. “When you fast, you eliminate input of additional toxins from food,” says Dr. Katz, “and there is a potential biological...
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...In rural areas, milk may be processed fresh or sour. The choice depends on available equipment, product demand and on the quantities of milk available for processing. In Africa, smallholder milk-processing systems use mostly sour milk. Allowing milk to ferment prior to processing has a number of advantages and processing sour milk will continue to be important in this sector. Where greater volumes of milk can be assembled, processing fresh milk gives more product options, allows greater throughput of milk and, in some instances, greater recovery of milk solids in product. Because of differences between processing systems, each will be dealt with separately. The section on fresh-milk technology deals with techniques used for processing fresh milk in batches of up to 500 litres. Sour-milk technology is used for processing batches of up to 15 litres of accumulated sour milk. This will be described in the section on sour-milk technology. Fresh Milk Technology This section describes the manufacture of skim milk, cream, butter, butter oil, ghee, boiled-curd and pickled cheese varieties and fermented milks from fresh milk. The processing scale envisaged is 100 to 200 litres of milk per day. However, the processes described are suitable for batches of up to 500 litres per day. Most of the equipment described can be fabricated locally. Equipment not available locally, such as a milk separator, has a cost advantage and quickly gives a good financial return in terms of increased efficiency...
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