pH Measurement

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Morgan State University

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I will upload the data from our lab and the Lab report Guideline also the lab paper show the steps for the lab itself .

Our lab start from page 8 - 11 in Environmental Lab manual

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Environmental Engineering Laboratory Manual Morgan State University School Department of Civil Engineering CEGR 338 Environmental Engineering Lab 2 Table of Contents Background of Environmental Engineering ............................................................................. 4 Lab Safety Discussion............................................................................................................... 5 General Guidelines .............................................................................................................. 5 Glassware and Experiment ................................................................................................ 6 Chemical Handling.............................................................................................................. 6 Heating Procedures ............................................................................................................. 7 Accidents and Injuries ........................................................................................................ 7 Personal Safety .................................................................................................................... 7 1. pH Measurement .............................................................................................................. 8 2. Salinity (Hydrometric Method) ...................................................................................... 12 3. Settleable Matter / Total Solids ...................................................................................... 18 4. Total Dissolved and Suspended Solids Dried at 103-105 C / Fixed and Volatile Solids Ignited at 550 C ........................................................................................................................... 21 5. UV-Vis Spectroscopy..................................................................................................... 26 3 Background of Environmental Engineering Environmental engineering developed from the historical branch of civil engineering know as sanitary engineering involving drinking water and water treatment. The field was defined in 1955 by Kilcawley, Pincus and Burden of Rensselaer Polytechnic Institute (RPI) as “…that portion of the science of environmental control in which engineering is used to conserve and develop the world’s resources for the general well-being of man as measured by such indices as the absence of disease, comfort, convenience and productivity.” Environmental engineers develop solutions to environmental problems utilizing the principles of biology and chemistry. Environmental engineers are involved in water and air pollution, recycling, waste disposal, and public health issues. They design municipal water supply and industrial wastewater treatment systems. The U.S. Department of Labor, Bureau of Labor Statistics projects that jobs for environmental engineers will grow by 25% from 2006 to 2016... 4 Lab Safety Discussion Safety is the responsibility of every student. This includes personal safety and the safety of your fellow students. REMEMBER TO THINK before you ACT… There are various safety programs, which are adequate and assist in reducing accidents, however, the benefits obtained from the use of common sense can outweigh the benefits from any safety rules. REMEMBER ALWAYS: THINK before you ACT!!! General Guidelines 1. All students should conduct themselves in a responsible manner at all times in the laboratory environment. 2. All written and verbal instructions should be followed carefully. Ask instructor immediately before proceeding with a part of procedure, if you did not understand directions. 3. Do not work in laboratory without instructor present or proper instruction. 4. Do not touch any equipment, chemicals or experimental materials until properly instructed to do so. 5. Be prepared for laboratory experiments by reading all procedures thoroughly before commencing with the experiment. 6. Do not eat food, drink beverages, or chew gum during lab experimentation. 7. Perform only the experiments designated by the instructor. Unauthorized experiments are prohibited. 8. Work areas should be clean and tidy at all times. 9. No horseplay, practical jokes, and pranks are dangerous and prohibited. 10. Cell phone operation should not be conducted during lab experimentation. 11. Know locations of the proceeding: 5 a. First aid kit b. Eyewash station c. Safety shower d. Fire extinguisher e. Fire alarm and exits 12. Wash hands after all spills and at the end of the lab. 13. Examine all equipment for any defect before using. 14. Do not leave experiments in process unattended. 15. ALL INSTRUCTIONS, ORAL OR WRITTEN, MUST BE FOLLOWED AT ALL TIMES. Glassware and Experiment 1. 2. 3. 4. 5. 6. 7. 8. 9. Never assume glassware is clean; wash at the beginning and end of each lab session. Examine all equipment for defects before using. Do not pipette or siphon lab chemicals by mouth, use rubber bulb or pipette pump. Carry glass tubing in vertical position to minimize the likelihood of breakage and injury. Always protect your hands with proper material when inserting glass tubing into, or removing it from, a rubber stopper. Fill wash bottle with distilled water only and use as instructed. Never use chipped or cracked glassware for lab experimentation purposes. Do not immerse hot glassware into cold water, possibility of shattering. Contact instructor if you do not understand the operation of a piece of equipment. Chemical Handling 1. 2. 3. 4. 5. 6. Notify instructor if hazardous material are observed. Never mix chemicals together unless instructed to or experiment indicates. Do not touch, taste, nor smell any chemicals, unless specifically instructed. Check labels carefully before removing contents from container. Never return unused chemicals to their original containers. Acids should be handled with extreme caution and care.  Always add acid to water, swirl or stir solution and notice heat produced, especially sulfuric acid.  Care should be observed when transferring acids from one section of the lab to another. 7. Never remove chemicals or other materials from the laboratory environment. 8. Hold container away from body when transferring reagents from one container to another. 6 Heating Procedures 1. 2. 3. 4. Never leave heated burner unattended. Never leave anything being heated unattended. Always turn hot plate or burner off when finished. Do not point the open end of a test tube being heated at self or anyone else in lab environment. 5. Never peer into a container you are heating. 6. Do not place heated materials directly on lab desk surface. Please use insulating pad. 7. Do not place any substances directly into heater flame unless directed by instructor. Accidents and Injuries 1. Report all accidents, no matter how minor, immediately to instructor. 2. If chemicals are spilled or splashed in eye(s) or skin flush immediately with water from safety shower or eyewash station for at least 20 minutes. 3. If mercury thermometers or instruments with mercury are broken, the mercury must not contact skin. 4. Skin burns: Immediately place affected area under cold running water for 5-10 minutes to remove the heat or irritant. 5. Hair or clothing fire: To extinguish the flames use the safety shower. 6. If inhale chemical irritants –close containers, open widows or otherwise increase ventilation. 7. Ingestion of chemicals-immediately report to Health Center. 8. Notify the appropriate authorities immediately in case of fire at 911. 9. If clothes catch fire drop to the floor and roll to smother the fire. 10. If fire is large and spreading, activate the fire alarm to alert building occupants. 11. Evacuate building in appropriate manner. Personal Safety 1. 2. 3. 4. Please wear proper eye protection---goggles at all times. Wear appropriate lab coat or lab apron while in lab environment. Do not wear contact lens during lab experiments. Please wear shoes that do not have open spaces; sandals and open-toe shoes are not acceptable. 5. Confine long hair, neckties, jewelry and loose clothing while in lab environment. 7 1. pH Measurement 1.1 Introduction A very important measurement in many liquid chemical processes (industry, pharmaceutical, manufacturing, food production, etc.) is that of pH: which represents the hydrogen ion concentration in a liquid solution. The concentration of H¯¹ affects the solubility of inorganic and organic species, the nature of complex metal cations and the rates of chemical reactions. The concentration of the H¯¹ is frequently expressed as the pH of the solution rather than hydrogen ion molarity. pH is defined by the equation below: pH = log [H+¹] (1.1) In the equation above the logarithm is taken to the base. If [H¯¹] is 1 x 10¯4 moles per liter, the pH of the solution is 4. If [H+¹] = 1 x 10¯² M, the pH is 2. [H+¹] x [OH¯¹] = Kw = 1.0 x 10¯14 at 25ºC (1.2) The above equation shows the relation of pH in a basic solution. Since [H¯¹] equals [OH¯¹] in pure water, in equation 2, [H+¹] must be 1 x 10¯ 7M. Therefore, the pH represented in distilled water is 7. The solutions that exhibit [H¯¹] > [OH¯¹] are acidic and are denoted with a pH 7 applies when [H¯¹] < [OH¯¹] and a solution with a pH of 10 will have [H+¹] = 1 x 10-10 M and a [OH¯¹] = x 10-4M. Therefore, a solution with a high pH is called “caustic” and “acid”, if it exhibits a low pH. pH measurement can be determined experimentally in two ways. One is to use an indicator, a soluble dye whose color is sensitive to pH. Indicator colors change over a relatively short (about 2 – unit) pH range. When properly chosen, they give the approximate pH of solutions. Two common indicators are litmus, usually used on paper, and phenolphthalein, commonly used in acid-base titrations. Litmus changes from red to blue in the pH range 6 to 8. Phenolphthalein changes from colorless to red on the range 8 to 10. Any one indicator is useful for determining pH only in the region where it changes color. Indicators are available for measuring pH in any part of the scale. Universal indicator papers, which contain a mixture of several indicators and change color over a wide pH range, are also in common use. An electronic pH meter is used for more precise measurements of pH from the electrical potential between two electrodes in a solution. The potential varies with pH and activities an 8 analog or digital meter calibrated to read pH directly to the nearest 0.01 or 0.001 unit. A pH meter is used when reliable knowledge or control of pH is necessary. Solutions, which undergo only a small change in pH when small quantities of acid or base are added, are called buffers. A buffer solution can be prepared from approximately equal amounts of a weak acid and its salt with a strong base or from a weak base and its salt with a strong acid. Figure 1-1. pH meter(left) and typical pH Probe Design(right) The qualitative determine of the pH value of foodstuffs is probably the oldest analysis method in the world. All foodstuffs are tested with taste organs. Thereby some are noticed to be acidic and some to be alkaline. With modern pH electrodes these taste sensations can be measured in exact figures, i.e.: Cold beverages………………………………………pH – 2.8 Fruit vinegar…………………………………………pH – 3.2 Orange juice…………………………………………pH – 3.7 Beer………………………………………………….pH – 4.4 Coffee………………………………………………..pH – 5.0 Milk………………………………………………….pH – 6.6 Distilled water……………………………………….pH – 7.0 (neutral) Baking Soda ……………………..………………….pH – 8.3 9 1.2 Calibration of pH probe 1. Calibrate the pH probes with the given buffer solution of 4, 7 and 10 followed the calibration procedures given a separate sheet. 1.3 pH reading from buffer solutions Procedure 1. Remove probe from the aqueous solution and carefully rinse the probe with distilled water 2. Gently wipe probe with designated wipes 3. Carefully place probe into designated buffer solution for calibration 4. Allow probe to stabilize and record the temperature and pH of the solution 5. Remove probe and carefully rinse with distilled waster 6. Place probe back into its aqueous solution base 7. Follow steps 2 thru 6 for the other buffers (4,7, or 10) Table 1-1 pH of buffer solution Solution Beaker 1, Buffer 4 Beaker 2, Buffer 7 Beaker 3, Buffer 10 Temperature (oC) Measured pH 1.4 pH measurement of unknown samples Procedure 1. 2. 3. 4. 5. Rinse the pH probe with distilled water and place it into the test sample Take 3 separate measurements of the pH of this sample of solution Record the data into the data sheet provided Repeat steps 1 thru 3 for the other samples provided Record data in provided data sheet 10 Table 1-2 pH of unknown samples Solution Temperature(oC) Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Measured pH 1.5 Lab Report 1. Identify the unknown samples based on your pH measurements and show chemical formula for each sample. 2. Discuss temperature effect on pH, 3. Calculate the concentration of HCL, one of unknown samples. 11 2. Salinity (Hydrometric Method) 2.1 Introduction Salinity is determined by measuring specific gravity with a hydrometer, correcting for temperature, and converting specific gravity to salinity at 15° C by means of density salinity tables. Salinity is usually expressed in parts per thousand (ppt). When measuring how much salt is in water or more accurately, when measuring salinity, it is reported in parts per thousand (ppt or ‰). The salinity of ocean water is about 35 ppt. Seawater has about 35 parts of salt per 1000 parts of water. In other words, if you had 1,000 grams of water and dry up all the water, you would be left with 35 grams of salt. This means the ocean is about 3.5% salts. Salinity is not the same in all bodies of water. Most rivers, ponds, and streams have almost no salts with salinity ranging from 0-5 ppt. This range of measurement is considered fresh water. In an estuary (bay), the flow of fresh water from streams and rivers mixes with salty ocean water. That mixture is called brackish water, with a range of salinity from .05 to 30 ppt. In the Red Sea, the water is considered brine, with salinity up to 50 ppt. This is the saltiest lake in the world---even saltier than the ocean! Drinking water is less than 0.5 ppt. The density of seawater is a function of both water temperature and salinity, thus if we measure both the temperature and the density of a water sample we should be able to determine its salinity. To determine density we could take an exact volume of water and weigh it, then divide the mass by the volume. Unfortunately, it is difficult to determine both mass and volume to the precision we desire with the laboratory equipment we have available to us. 12 Instead of measuring mass and volume directly, we return to Archimedes’ principle: “a floating body will displace a volume of water equal to its own mass.” If we use a fixed mass that is less dense than the water sample, such as a hollow glass ball, it will sink down into the water until it displaces its mass. The greater the density of the water the higher the sphere will float. Hydrometers are devices designed to measure fluid density. The hydrometer’s mass is precisely fixed and it is concentrated at the bottom of the tube (like a buoy) so that the hydrometer will always float upright. The narrow stem is precisely graduated so that as the device sinks and displaces its own mass, the level to which it sinks is equal to the seawater density. As density of the seawater increases, the volume of the displaced seawater decreases (the hydrometer sinks less in the higher density fluid). Table 2-1 List of bodies of water by salinity Name A Salty Lake (like the Red Sea) The Ocean Mouth of estuary by a river Entrance of estuary by the ocean Tidal fresh river Freshman Stream or River Salinity 36 – 50 ppt 30 – 35 ppt 1 – 15 ppt 15 – 30 ppt .05 – 14 ppt < 1 ppt Types of water based on amount of dissolved salts in parts per thousand (ppt): Fresh water 50 ppt 2.1 Determination of Salinity by Evaporation As we have defined salinity as the total mass of dissolved salts (measured in grams) in one kilogram of seawater, the most straightforward way to measure salinity is to measure exactly one kilogram of seawater, evaporate the water, and weight the salt that precipitates out. Evaporating a full kilogram of water would take more time than we have today however, so we will shorten the process by evaporating a small fraction of a kilogram. Procedure 1. Label three 250 mL beakers for the three samples. Fill each beaker to about 200 mL, while making certain that you have the correct sample in each labeled beaker. 13 2. Label three evaporating dishes (with the same labels as the sample beakers) and weigh each to the nearest 0.01 gram. Record the masses of the dishes, M1. 3. Using a pipette, transfer about 10 mL of each of the three salt solutions to the corresponding labeled evaporating dishes. Weigh each evaporating dish with the water to the nearest 0.01 gram and record the masses, M2. Determine the mass of the water samples by subtracting the weight of the dish only, and record the masses, Mw=M2-M1. 4. Carefully bring the evaporating dishes to oven at the rear of the room and carefully place them in the drying oven. Leave them in the oven until dry – this will take the majority of the lab period. 5. Once the samples are dry allow them to cool for a few minutes, then weigh each evaporating dish and record the results on the data sheet (dish + salt), M3. Subtract the masses of the dishes to determine the mass of each of the salt samples and record the results, Ms=M3-M1. 6. Determine the salinity of each sample using equation 1 (below). 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒔𝒂𝒍𝒕 Salinity = 𝒘𝒆𝒊𝒈𝒉𝒕 𝒐𝒇 𝒘𝒂𝒕𝒆𝒓 x 1000 ‰ (2.1) Table 2-2 Salinity by evaporation Sample 1 Weight of evaporating dish, M1 (g) Weight of evaporating dish and water, M2 (g) Mass of water, Mw=M2-M1 (g) Weight of evaporating dish and salt, M3 (g) Mass of salt, Ms=M3-M1 (g) 𝑀 Salinity = 𝑀 𝑠 × 1000 ‰ 𝑤 2.2 Determination of salinity using the hydrometer Equipment: 1. Hydrometer jar – Use a 1000 mL graduated cylinder 2. Thermometer – graduated in 0.2 C divisions 3. Samples – Use set of 3 unknown samples of various grams of NaCl The National Bureau of Standards for specific gravity of NaCl solutions should calibrate hydrometers at 15 / 4 C. 14 Procedure: 1. Fill the hydrometer jar (1000 mL graduated cylinder) with sample. 2. Hang the thermometer into the cylinder while the jar is sitting in the vertical position. Make certain the thermometer is totally immersed and you can read it through the side of the cylinder. 3. Carefully remove the hydrometer from its enclosure and insert it into the cylinder, until it begins to float then give it a slight twist to remove bubbles. **Caution: Make sure that the hydrometer does not hit the bottom hard (it may break). Also, take care that drops of water do not splash onto the hydrometer stem above the water level. 4. Read and record the temperature of sample to the nearest 0.5 C. 5. Read and record the specific gravity from the scale on the hydrometer stem to the nearest 0.001 (estimate three decimal place). 6. Repeat procedure 3 times and obtain average of each. Precautions in using hydrometer: 1. Avoid dried salt from previous use 2. Avoid grease from fingerprints 3. Avoid water droplets on the portion of the stem not submerged. This will throw off your results. Accuracy in reading hydrometer: 1. Take the readings without touching the hydrometer 2. Take readings with your eyes at the same level as the water surface in the hydrometer cylinder. Viewing the scale up or down at an angle can give an incorrect reading. **Read at the point where the flat-water surface would cross the hydrometer stem. Notice that the water curves up slightly next to the wall of the stem (the curve is a meniscus). Make sure you measure your results from the bottom of the curve, not the top. 3. Read the specific gravity at the 4th decimal place using the lines printed between the labeled graduations. 15 Figure 2-1 Hydrometer Reading 4. Make temperature corrections for specific gravity reading from factors listed in Table. Table 2-3 Salinity by Hydrometer method (Sample 1) Temperature (°C) Specific Gravity of Sample Trial 1 Trial 2 Trial 3 Average Salinity (‰) Salinity (‰) 16 Reading chart: 1. Run horizontally across the table until you find the column for the temperature at which you took the reading. 2. Run down the column until you get to the row for the specific gravity you recorded. 17 3. Settleable Matter / Total Solids 3.1 Introduction Residue refers to solid matter suspended or dissolved in water or wastewater. Residue may affect water or effluent quality adversely in a number of ways. Waters with residue generally are of inferior palatability and may induce an unfavorable physiological reaction in the transient consumer. Highly mineralized waters also are unsuitable for many industrial applications. For these reasons, a limit of 500 mg residue/L is desirable for drinking waters. Waters with very high levels of nonfiltrable residues may be aesthetically unsatisfactory for such purposes as bathing. “Total residue” is the term applied to the material left in the vessel after evaporation of a sample and its subsequent drying in an oven at a defined temperature. Total residue includes “nonfiltratable residue”, that is, the portion of total residue retained by a filter, and “filterable residue”, the portion of total residue that passes through the filter. Conductivity measurements are approximately proportional to the filterable residue and may be used in selecting proper sample size for residue determinations. However, close correlations of results of the two are not always obtained. An additional possibility for checking fixed filtratable residue is by use of ion-exchange procedures. Selection of drying temperature Residues dried at 103 to 105 C may retain not only water of crystallization but also some mechanically occluded water. Loss of CO will result in conversion of bicarbonate to carbonate. 18 Loss of organic matter by volatilization usually will be very slight at this temperature. Because removal of occluded water is marginal at 150 C, attainment of constant weight is very slow. Residues dried at 180 +/- 2 C will lose almost all mechanically occluded water. Some water of crystallization may remain, especially if sulfates are present. Organic matter is lost by volatilization but is not completely destroyed. Bicarbonates are converted to carbonates and carbonates may be decomposed partially to oxides or basic salts. Some chloride and nitrate salts may be lost. In general, evaporating and drying water samples at 180 C yields values for total residue closer to those obtained through summation of individually determine mineral species than the values for total residue secured through drying at a lower temperature. Settlable Matter A well-mixed sample is evaporated in a weighed dish and dried to constant weight in a 103 to 105 C. The increase in weight over that of the empty dish represents the total residue. Although the results may not represent the weight of actual dissolved and suspended solids in wastewater samples, the determination is useful for plant control. In some instances, correlation may be improved by adding 1N sodium hydroxide (NaOH) to wastewater samples with a pH below 4.3 and maintaining the pH of 4.3 during evaporation. Correct final calculation for added sodium.  Exclude large, floating particles or submerged agglomerates of non-homogenous materials from the sample. Disperse visible floating oil and grease with a blender before withdrawing a sample portion for analysis. 3.2 Equipment 1. 2. 3. 4. 5. 6. 7. 8. Evaporating dish – porcelain Drying oven, for operation at 103 to 105 C Desiccator Analytical balance Imhoff cone Graduated cylinder Dish tongs Distilled water 19 3.3 Total Soilds, by weight Procedure 1. 2. 3. 4. 5. 6. 7. 8. Preheat an evaporating dish at 103-105 C for 1 hr. Remove evaporating dish from oven and place in desiccator. Weigh the porcelain dish. Mix sample well and add 15 mL the pre-weighed dish. Rinse any residue with distilled water. Place the sample in a preheated oven. Dry at 103 – 105 C Cool in a desiccator and weigh Table 3-1 Total Solids, by weight Sample 1 Weight of evaporating dish, M1 (g) Sample volume, Vs (ml) Weight of evaporating dish and residue, M2 (g) Total residue, Ms=M2-M1 (g) 𝑀 Total residue/L = 𝑉𝑠 × 1000 (g/L) 𝑠 3.4 Settleable Matter, by volume Procedure 1. 2. 3. 4. 5. Mix sample well and pour into Imhoff cone to the 1000 mL mark. Wait 45 minutes for the sample to settle. Gently stir mixed sample along the sides of the cone. Wait an additional 15 minutes for sample to settle. Record readings at the top of the solids layer of the Imhoff cone as the mL/L settable matter. Note: If there are pockets of clear water in the settled material, subtract the estimated volume of the pockets from the volume of the settled matter. Table 3-2 Settleable Matter, by volume Sample 1 Volume of sample, Vs (ml) Volume of pockets of liquid (if applicable), Vp (ml) Volume of settleable matter, Vm (ml) Total settleable matter, by volume = 𝑉𝑚 −𝑉𝑝 𝑉𝑠 × 1000 (ml/L) 20 4. Total Dissolved and Suspended Solids Dried at 103-105 C / Fixed and Volatile Solids Ignited at 550 C 4.1 Introduction The term “solids” is generally used when referring to any material suspended or dissolved in wastewater that can be physically isolated either through filtration or evaporation. Solids can be classified as either filterable or nonfilterable. Filterable solids may either be settleable or nonsettleable. Solids can also be classified as organic or inorganic. “Filterable” solids are so small that they will pass through a standard laboratory filter, while “nonfilterable” solids are large enough to be captured on a standard filter pad. The nonfilterable solids are termed “settleable” if the solids settle out in a standard laboratory-settling container within a specified period of time. They are called “non-settleable” if they fail to settle out within that time period. If solids are “organic”, the material is carbon-based and will burn. “Inorganic” solids, on the other hand, are mineral based and generally will not burn. Any material that was at one time living (for example: body wastes, starches, sugar, wood, bacteria and cotton) is allorganic, whereas limestone, iron and calcium are inorganic. Total nonfilterable residue is the retained material on a standard glass-filter after filtration of a well-mixed sample. The residue is dried at 103 to 105 C. If the suspended material clogs the filter and prolongs filtration, the difference between the total residue and the total filterable residue provides an estimate of the total nonfilterable residue. Volatile nonfilterable residue and fixed nonfilterable residue can be determined on the material retained on the glass-fiber filters in the evaporating dishes on completion of the drying process at 103 to 105 C. 21 The amount of solids in wastewater is frequently used to describe the strength of the waste. The more solids present in a particular wastewater, the stronger that wastewater will be. If the solids in wastewater are mostly organic, the impact on a treatment plant is greater than if the solids are mostly inorganic. Normal domestic wastewater contains a very small amount of solids when compared to the amount of water that carries it, generally less than 0.1%. This can be misleading, however because it may take only a very small amount of organic residue to create large pollution problems. The number and severity of pollution problems will depend on the type of solids that are involved. As a general rule, large quantities of organic solids will create more pollution problems than will the same quantity of inorganic solids. Therefore, not only is it important to know how much solids are present in the waste, but also the type of solids that are present. The test procedures for solids provide essential information about the level and type of solids coming into the treatment plant and whether the solids are actually being removed in the plant processes. Terminology a. Filtration – removal of suspended matter by passing a sample through a porous matrix (such as a filter pad) that prevents participles from getting through. b. Fixed solids – those solids (total, suspended or dissolved), which remain after ignition for 15 – 20 minutes at 550 C +/- 50 C. These are also commonly referred to as ash. In general, fixed solids are made up of inorganic material. c. Total dissolved solids – this term refers to those solids that will pass through a standard glass fiber filter. d. Total solids – the term refers to the material left in a dish after evaporation of a sample and its subsequent drying in an oven at a defined temperature. Total solids include “Total Suspended Solids” and Total Dissolved Solids”. e. Volatile solids – solids which are lost during ignition (by burning) for 15 – 20 minutes at 550 C +/- 50 C. In general, volatile solids are made up of organic material. 22 4.2 Equipment 1. 2. 3. 4. 5. 6. Tongs/oven gloves Evaporating dishes Filter paper Funnel Filter flask Graduated cylinder 7. Muffle oven 8. Desiccator 9. Mechanical convention oven 23 4.3 Total Dissolved and Suspended Solids Dried at 103°C - 105°C Procedure: 1. 2. 3. 4. 5. 6. 7. 8. 9. Heat evaporating dish to 550 C in muffle oven for 1 hr. Remove and place dishes in air to cool. Place dishes in desiccator and weigh the cooled dish before use. Obtain and weigh filter paper from package Place filter paper into the funnel assembly on the lab bench. Obtain and mix well an unknown sample to obtain a more uniform participle size. Pour 15 mL of sample in graduated cylinder into funnel. Rinse a 10 mL portion of distilled water into funnel, if needed. While waiting for completion of filtration, remove the porcelain dish from the desiccator and weigh. 10. Transfer filtrate to porcelain dish after sample filtering is complete. 11. Transfer filter to porcelain dish after sample filtering is completed. 12. Weigh sample before and after placing into oven to dry at 103 to 105 C for 1 hr. 13. Later cool sample in the desiccator and weigh. 4.4 Fixed and Volatile Solids Ignited at 550°C Procedure: 1. Place weighed sample and filter into 550 C muffle oven for 15 minutes. 2. Carefully remove sample and filter from muffle oven and cool in air. 3. Weigh sample and filter after cooling and record data. **Caution Oven Is HOT!! 24 Table 4-1 Total Dissolved/Suspended Soilds of Sample 1 Sample Volume, VS (ml) Dissolved(Filterable) Solids Weight of evaporating dish for liquid sample, ML1 (g) Weight residue after oven for liquid sample(105 C ), ML2 (g) Weight of residue after furnace for liquid sample (550 C), ML3 (g) Total Volatile Dissolved Solids, 𝑇𝑉𝐷𝑆 = Total Fixed Dissolved Solids, 𝑇𝐹𝐷𝑆 = Total Dissolved Solids, 𝑇𝐷𝑆 = 𝑀𝐿2 −𝑀𝐿3 𝑉𝑠 𝑀𝐿3 −𝑀𝐿1 𝑀𝐿2 −𝑀𝐿1 𝑉𝑠 𝑉𝑠 × 1000 (g/L) × 1000 (g/L) × 1000 (g/L) Suspended Solids Weight of evaporating dish for filter, MF1 (g) Weight of filter, MF (g) Weight residue after oven for filter(105 C ), MF2 (g) Weight of residue after furnace for filter (550 C), MF3 (g) Total Volatile Suspended Solids, 𝑇𝑉𝑆𝑆 = Total Fixed Suspended Solids, 𝑇𝐹𝑆𝑆 = Total Suspended Solids, 𝑇𝑆𝑆 = 𝑀𝐹2 −𝑀𝐹3 𝑀𝐹2 −(𝑀𝐹1 +𝑀𝐹 ) 𝑉𝑠 × 1000 (g/L) 𝑉𝑠 𝑀𝐹3 −(𝑀𝐹1 +𝑀𝐹 ) 𝑉𝑠 × 1000 (g/L) × 1000 (g/L) Total Solids Total Solids, TS = TDS + TSS (g/L) 25 5. UV-Vis Spectroscopy 5.1 Introduction Objective Review basic analytical chemistry skills, including solution making, transferring and linear diluting. Understand the error involved and error propagation. Materials: Methylene Blue C16H18ClN3S, MW 319.85.Also called Swiss blue. One gram dissolves in about 1000 ml of water. Peak absorption at 369 nm 5.2 Create Calibration Curve from standard solutions Procedures: 1. 2. 3. 4. 5. Weigh 500mg dye on electric balance Dissolving all the solid dye in beaker Transfer all the solution into a 500ml volumetric flask Fill up the volumetric flask to the tick mark Prepare standard solutions of 500, 200, 100, 50 and 20 ppm from 1000 ppm stock solution Table 5-1 Preparation of standard solutions STD PPM Stock DI water Total Volume 20 0.2 9.8 10ml 50 0.5 9.5 10ml 100 1 9 10ml 200 2 8 10ml 500 5 5 10ml 6. Vortex vial to complete mix 7. Transfer Standard solutions to cuvette 26 8. Measure the transmissivity at a peak measure three times and make a note of your results in your lab notebook 9. Create calibration curves from data. Table 5-2 Absorbance of standard solutions PPM Wavelength 1 Absorbance 2 Average 20 50 100 200 500 UV/VIS Absorbance 1 0.8 0.6 0.4 0.2 0 0 50 100 150 200 250 300 Concentration (ppm) 350 400 450 500 Figure 5-1 Calibration curve from standard solutions 5.3 Two steps of a serial dilution and measure the concentrations of unknown samples 1. Pour about 11 ml unknown concentration of methylene blue solution from the bottle to your vial 2. Dilute the dye solution 10 fold by using pipettes : Pipette 1 ml above sample solution to your vial 3. Fill the solution to 10 ml 4. Transfer Standard solutions to cuvette 5. Measure absorbance of each 27 Figure 5-2 Serial Dilution of unknown samples Table 5-3 Absorbance of unknown samples Absorbance Serial Dilution 1 1/10 Sample 1 Sample 2 Sample 3 1/100 Wavelength Instrument Use 1. Power on instrument (switch is on left side). 2. Turn on monitor and double-click ‘Cary win UV’ 3. Instrument will run through a start-up check for about 1 minutes. 4. In the toolbar frame, select the ‘Concentration’ icon. 5. In dialog box, enter wavelength 369 nm. a. Choose Abs (absorbance). b. Replicate is 2 6. Click on ‘Standard’. a. unit : mg/L b. number of standard and concentration of standard solution 7. Click on ‘Sample’ and enter sample number 8. Click ‘OK’ 9. Click on Zero icon after insert Blank cuvette into UV slot. 10. Fill cuvette ¾ with standard samples and cleaning cuvette surface with chem wipes. 11. Place cuvette in the slot. 12. Click ‘Start’ 13. Record Abs(absorbance) 14. Drawing standard graph 15. Fill cuvette ¾ with unknown samples and cleaning cuvette surface with chem wipes. 16. Place cuvette in the slot. 17. Click ‘Start’ 18. Record concentrations 28 Lab report requirement o Calculate solution concentration by ppm for all solutions o Discuss source of data errors o How do you improve your skill to get better accuracy and precision of solution making o Describe the key steps of the experiment o Attach all the original data and spectrum 29 -1 in a pH = -log Lab Coat a = -14 Lab 1. pH Measurement. [ ] concentration pH? [ht] in CH+]= 10 liquid solution (pH = ( Lab Notebook &. [H+] PH- ) [H+] = ? log C y Caba PH=14 acidic | = basic -1= log [Ht [+] = 10-'m 1.3 Calibrationchef using buffer soln (pt=4,7,10) 1.4 pH Measurement of 5 unknown samples ( Vinegar, water, soda, Baking Soda, Hce) [ (H+) = 10 M pH (1 in \-1 pH 71 724 neutral pH=7 - lag [ft] objective procedures Data / Resulto Summary Check Report average pt &Identify unknown samples Show chemical formula for each temperature effect on PH PH H Calculate [HI] Red the blue 9 PH 4 Yellow T/ TIP 20.487.04 PH7 T T PHo 20020 4.05 19-89 9.75 Baking soda Hel water PH for a Virger PH fors PH for 2 sostal PH for 3 3 PH for 1 *8.30 #8-56 *8.71 +8.65 +3-19 *2.27 * 231 *2-32 *1-01 *0-97 *3.16 48-20 #6-95 *0.92 20-08 20.66 20.40 T:-21.26 20.0
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pH Measurement Lab Report
Introduction
The main purpose of this experiment was to determine the pH value of five unknown
samples vinegar, water, soda, baking soda and HCl. The pH measurement is very important in
chemical processes like in food production industries, pharmaceuticals and also in manufacturing
industries. pH represents the hydrogen ion concentration in a liquid solution. The hydrogen ion
concentration affects organic and the inorganic species concentration, nature of complex metal
cations and the rates of chemical reactions. The hydrogen ion concentration is frequently
expressed as the pH of the solution rather than hydrogen ion molarity. pH is defined by the
equation below:
pH = −log [H+ ¹]
In the equation above the logarithm is taken to the base. If [H¯¹] is 1 x 10¯ 4 moles per liter, the
pH of the solution is 4. If [H+ ¹] = 1 x 10¯² M, the pH is 2.
[H+ ¹] x [OH¯¹] = Kw = 1.0 x 10¯ 14 at 25ºC

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The above equation shows the relation of pH in a basic solution. Since [H¯¹] equals
[OH¯¹] in pure water, in equation 2, [H+ ¹] must be 1 x 10¯ 7M. Therefore, the pH represented in
distilled water is 7. The solutions that exhibit [H¯¹] > [OH¯¹] are acidic and are denoted with a
pH 7 applies when [H¯¹] < [OH¯¹] and a solution with a pH of ...


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