...Buffer solutions and common ion effect A buffer solution resists (or buffers) a change in its pH. That is, we can add a small amount of an acid or base to a buffer solution and the pH will change very little. How to calculate pH of buffer solution containing both acid and conjugate base? Dissociation constant definition 1.1 can be rearranged into [pic] or [pic] (note that due to sign change [A-] was moved to nominator). This is so called Henderson-Hasselbalch equation (or buffer equation). It can be used for pH calculation of solution containing pair of acid and conjugate base - like HA/A-, HA-/A2- or B+/BOH. For solutions of weak bases sometimes it s more convenient to use equation in the form [pic]15.3 Two common types of buffer solutions are : (1) a weak acid together with a salt of the same acid with a strong base. These are called Acid buffers e.g. CH3COOH + CH3COONa. (2) a weak base and its salt with a strong acid. These are called Basic buffers. e.g.NH4OH + NH4Cl. Let us illustrate buffer action by taking example of a common buffer system consisting of solution of acetic acid and sodium acetate (CH3COOH/CH3COONa). CH3COOH --- H+ + CH3COO– CH3COONa ---- Na+ + CH3COO- since the salt is completely ionised, it provides the common ions CH3COO– in excess. The common ion effect suppresses the ionisation of acetic acid. This reduces the concentration of H+ ions which means that pH of the solution is raised. Thus, a 0.1 M acetic acid solution has a pH...
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...pH Measurement and Buffer Preparation Quilao, M.H., Regua, R., Reinoso, L.A., Rojas, K.J., Sabalberino, E.M. Abstract In this experiment, phosphate buffer solution was prepared and the pH of the buffer and samples were determined through different liquid indicators and the pH meter. Also, the buffer capacity of the prepared buffer solution was calculated. The group was tasked to prepare a 250 mL phosphate buffer solution of pH 8.0 using dihydrogen phosphate ion (H2PO4) and primary sodium phosphate monohydrate (NaH2PO4.H2O). With the aid of 6.0 M HCl and 6.0 M NaOH, the pH of the buffer was adjusted while being recorded by the pH meter until it reached the desired pH. Afterwards, the buffer solution was introduced to Colorimetric Determination which used acid-base indicators. The buffer solution changed to color yellow when Thymol and Methyl red were added, blue when Bromophenol blue and Bromocresol green were included, purple for Bromocresol purple, pink for Phenol red and Phenolphthalein, and orange for Methyl orange. Introduction The measurement of the low concentration of hydrogen ions present in any biological process is expressed as pH. pH is used to measure the acidity and alkalinity of a solution. pH involves ionic activity, making it difficult to accurately predict the pH value of a solution. The pH is also known to greatly affect our biological system and any large changes could be dangerous, which is why there is a buffer present within our systems...
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...Introduction Buffer is a solution that resists a change in pH when bases or acid are added. Solutions that are acidic contain high concentrations of hydrogen ions (H+) and have pH values less than seven. Buffer usually consist of a weak acid, and its conjugate base or a weak base and its conjugate acid. The function of buffer is to resist the changes in hydrogen ion concentration as a result of internal and environmental factor. This buffer experiment is important so that we relies the important of buffer in our life. Besides that, it is also important so that we master the buffer preparation techniques and can conduct the experiment ourselves without anyone to instruct us. Other than that, we got to learn how to operate a pH meter and we...
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...General Chemistry II Professor: Dr. Yang Yang Turned in: April 9, 2014 Experiment #6 The Properties of Buffers Abstract In this experiment the pH of fours solutions was recorded and identified as acidic, basic, or neutral. A buffer system of 0.10 M ammonium ion (NH4+) and 0.10 M ammonia (NH3). This buffer was made three times: once with equal parts ammonium ion and ammonia, next it was diluted to double the volume, and finally it was prepared with an addition of HCl. The pH was recorded to calculate the Ka and pKa values. The most accurate Ka value recorded was the second from B2 which was 5.13x10-10. Using this Ka value the appropriate volumes of ammonium ion and ammonia were calculated to make a buffer solution with a pH of 8.7. The final volumes were 15.9 mL of ammonium ion and 4.1 mL of ammonia. Part A solution pH acidic, basic, neutral? 0.100 M NaHSO4 1.8 acidic 0.100 M Na2CO3 11.2 basic 0.100 M NH3 10.9 basic 0.100 M NaCI 6.8 neutral Net Ionic Reaction NaHSO4 Na+ + HSO4- + H2O --> Na+ (SO4)2- + H3O+ HSO4- + H2O --> (SO4)2- + H3O+ Na2CO3 Na2CO3 + H2O --> NaHCO3 + NaOH 2Na+ + CO32- + H2O --> Na+ + HCO3- + Na+ + OH- CO32- + H2O --> HCO3- + OH- NH3 NH3 + H2O --> NH4-+ OH- NaCI NaCI + H2O --> H2O + Na+ + Cl- NaCI--> Na+ + Cl- Part B calculations attached on next page Ka Values Part Ka pKa B1 6.3x10-10 9.2 B2 5.13x10-10 9.29 B3 3.98x10-10 8.4 Discussion: All of the Ka values were...
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...CHAPTER 3: METHODOLOGY 3.1 Study Design This research is an experimental study which was conducted to investigate the effectiveness of treatment of Cassia alata as antioxidant effects in cardiovascular system of hyperglycemic rats. The antioxidant activity was tested from the leaf of Cassia alata using its aqueous extract. For this study, 30 Wistar rats weighing between 180 to 200g were used. They were housed in standard cages in a room with a 12 hour light/dark cycle and 50 to 60% relative humidity at a temperature of about 30°C. The animals had fed with standard food and water without limit. This study was conducted in two groups of streptozotocin (STZ) induced diabetic rats in which each group will consist of 15 rats. For the first group of STZ induced diabetic rats had fed with Cassia alata aqueous extract for 20 days meanwhile for the second group of STZ induced diabetic rats had fed with normal saline as a negative control for 20 days. The two groups of STZ induced diabetic had divided into 2 batches. First batch of diabetic rats was consisted of 6 rats for both groups while the second batch was consisted of 9 rats for both groups. All of the rats in two groups had fasted for 12 hour before induced diabetic via STZ injection. After an injection, the rats with level of fasting blood sampling (FBS) above 200 mg/dl will take for further investigation. Henceforth, the treatment was began in which the Cassia alata aqueous extract will administer orally after 48 hour diabetic...
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...Soil and crop factors can be managed for maximum and economical production * Table: major factors affecting yield potential The Law of the minimum * Crop yield is determined by the most limiting factor * Crop yield can only be increased by eliminating the most limiting factor * Yield cannot be increased by increasing the supply of other nutrients and factors * Challenge is to identify the limiting factors and eliminate them Sources of mineral nutrients for plant uptake * Plants take up mineral nutrients from soil solution * Amounts of nutrients in solution are small * Soil solution nutrients are replenished by there in soil/solid form Table: Nutrient dynamics in the soil that affect nutrient supply to plants The intensity factor of nutrient supply is the nutrient concentration in soil solution Quantity Factors * Is the amount of nutrient adsorbed on soil surfaces that can replenish the soil solution Nutrient buffering capacity * Ability of a soil to re supply a nutrient to the soil BC is described by the change in the amount of an ion adsorbed (∆Q) as a result of the change in soil...
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...lead to denaturation of the enzyme and the change in shape of the active site. (http://www.nuffieldfoundation.org/practical-biology/investigating-effect-ph-amylase-activity) Variables: Independent: The pH of the buffer solution. Dependent: The time taken for the solution to turn an opaque (lighter) blue from dark blue. Controlled: The volume of iodine solution; the volume of starch solution; the volume of buffer solutions; the volume of amylase solution; the temperature at 40°c; the time it is left in the water bath; and the concentration of the solutions. I will be using a water bath to keep the temperature constant, and to manipulate my independent variable, I will be using pH 4, 5, 7, 9, 10 by adding different pH buffer solutions with the amylase. * 50ml Amylase solution * 100ml Starch solution * 100ml Buffer solutions with pH 4, 5, 7, 9, 10 * 20ml Iodine solution Apparatus: * Test tubes x15 * Test tube racks * Boiling tubes x15 * Water bath * 50ml Burette ±0.1 * Pipette (dropper) * Stopwatch x5 Method: 1. Prepare a water bath at 40°c. 2. Prepare 5 test tubes and label them according to the range of pH. 3. In each of these test tubes, add in 2ml of amylase solution and 5ml of the buffer solution. Do this using a burette. 4....
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...This reaction is spontaneous for almost all esters but can be very slow under typical conditions of temperature and pressure. The reaction occurs at a much faster rate if there is a significant amount of base (OH-) in the solution. In this lab experiment, the rate of this reaction will be studied using an ester called para-nitrophenyl acetate (PNA), which produces an alcohol, para-nitrophenol (PNP). Question: What is the rate of reaction for the hydrolysis of PNA? What is the rate constant k? How are the rate of reaction and the rate constant k affected by varying (1) substrate PNA concentration, and (2) changes in pH (OH- base concentration) and addition of different nitrogen-containing base compounds (i.e.catalysts)? Hypothesis: I hypothesize that the rate of reaction and the rate constant for the hydrolysis of PNA can be determined experimentally to be first order. Also, in the reaction, the experiment will develop as follows: PNA +H2O --> PNP (yellow) + Ac Materials and Methods: The following solutions will be used in the experiment. 1. 0.2 M Phosphate Buffer, pH 6.5 (13.6 g KH2PO4 / 0.5 L, adjust to pH 6.5) 2. 0.4 M Phosphate Buffer, pH 6.5 (27.2 g KH2PO4 / 0.5 L, adjust to pH 6.5) 3. 2 M Potassium Hydroxide (11.2 g KOH / 100 ml solution) 4. 4(para)-nitrophenyl acetate (PNA), 0.0005 M (0.045 g /500 ml), store in 4 oC fridge. 5. Imidazole, 0.025 M (0.17 g Imidazole /100 ml); 6. Super 10x Imidazole, 0.25M (1.7 g /100 ml) 7. 2-Methylimidazole, 0.025...
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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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...dissociated in N/20 solution at 20o C. (6.34x10-5) 2. Calculate the hydrogen ion concentration in 10 liters of 0.1 N solution of an acid having dissociation constant 4.0x10-10 . (6.32x10-6g ion liter-1 ) 3. Nicotinic acid (Ka =1.4x10-5) is represented by the formula HNic. Calculate its percent dissociation in a solution which contains 0.10 mol of nicotinic acid per 2.0 liter of solution. (1.66%) 4. A certain weak acid has Ka=1.0x10-4. Calculate the equilibrium constant for its reaction with strong base. (1010) 5. 0.16 g of N2H4 are dissolved in water and the total volume made upto 500 ml. Calculate the percentage of N2H4 that has reacted with water in this solution. The Kb for N2H4 is 4.0x10-6M. (2%) 6. An aqueous solution of aniline of concentration 0.24M is prepared. What concentration of sodium hydroxide is needed in this solution so that anilinium ion concentration remains 1x10-3M? (Ka for C6H5NH3+ =2.4x10-5M) (10-2M) 7. An aqueous solution contains 10% ammonia by mass and has a density of 0.99g cm-3. Calculate hydroxyl and hydrogen ion concentration in this solution.(Ka for NH4=5.0x10-10M) (9.28x10-13 mol L-1) CALCULATION OF pH 8. Calculate pH value of (a) .00001M HCl solution, and (b) 0.04M HNO3 solution assuming complete...
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...Which of the following people would be most severely affected by prolonged vomiting? a. 3-year-old male b. 15-year-old male c. 35-year-old male d. 35-year-old female e. 50-year-old male 3-year-old male Extracellular fluid has a higher sodium content than intracellular fluid. The predominant intracellular cation is potassium. The predominant extracellular cation is sodium Which of the following fluid compartments contains the largest volume of water? a. plasma b. interstitial compartment c. intracellular compartment d. extracellular compartment e. lymph intracellular compartment Water moves back and forth across the plasma membrane by the process of osmosis One difference between the plasma and interstitial fluid is that the plasma has significantly more _____ than interstitial fluid. protein The distribution of sodium and potassium ions between intracellular and extracellular compartments is a. potassium mainly intracellular; sodium mainly in extracellular. b. sodium mainly intracellular; potassium mainly in extracellular. c. little of either intracellular but large amounts of both extracellular. d. equal amounts of both ions, in both intracellular and extracellular fluids. e. none of the above potassium mainly intracellular; sodium mainly in extracellular. Which of the following individuals would have the largest percentage of their bodyweight as water? a. a small 7-year-old female b. a lean 35-year-old male athlete c...
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...13B – Distribution and constituents of fluids P3: Distribution and constituents of body fluids – M2: Explain functions of the constituents of body fluids - Constituents of body fluid - The human body consists mostly of water, and is a major constituent to the human body and vital organs; of this 90% include blood plasma, lymph, urine, saliva, digestive juices, bile, cerebrospinal fluid and tissue fluid. Water enables substances to be transported throughout the body, red blood cells for example, as wells as supplying the medium required for metabolic reaction to take place (respiration). Without water the progression of these fluids would not be possible. Water is constantly being transported between the fluid compartments of the body. Water has five main functions in the body, of which includes: • 'Cell life - distribute nutrients to cells i.e. vitamins, minerals and glucose • Chemical and metabolic reactions - removal of waste products (toxins) from the organs • Transport of nutrients – participates in the breakdown of food • Body temperature regulation - water has a large heat capacity that allows it to help limit any changes to an individual's body temperature in a certain environment. For example the release of heat when the surrounding temperature is higher than body temperature • Elimination of waste' Urea – Urea is an organic molecule made up of carbon, nitrogen, oxygen, and hydrogen. Urea is a common constituent of blood and other various...
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...Abstract Buffer solutions were prepared and their pH measured to determine their buffering capacity. Three buffer solutions were utilized; an undiluted buffer, a diluted buffer solution with 10ml water and a diluted buffer solution with 18ml water. In the undiluted buffer solution there was minimal pH change with a high of 6.78 and a low of 6.47. In the buffer solution in which 10ml of water was added there was minimal pH change with a high of 6.78 and a low of 6.23. In the buffer solution in which 18ml water was added there was significant change in pH with a high of 6.1 and a low of 2.27. Introduction A buffer solution is a solution that is made up of water and a chemical which gives it unique properties with regard to its pH. The chemical is referred to as buffer agent. The buffer agent resists changes in pH when exposed to bases and acids. The aforementioned property makes it useful in dealing with various chemical accidents, protecting sensitive equipment and balancing internal processes of a number of living things. A buffer agent dissolved in water makes a buffer solution. It is constituted of (HA) an acid and a conjugate base (A-) mixed in water. Once there exists a chemical balance between HA and A- the addition of any bases or acids will be neutralized. This will result in little pH change of the solution. An increase in HA and A- as a result of the addition of bases or acids decreases the buffering capacity of the solution. This implies that the solution acts as...
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...Preparation of Buffers for Use in Enzyme Studies (by G. Gomori) The buffers described in this section are suitable for use either in enzymatic or histochemical studies. The accuracy of the tables is within ± 0.05 pH at 23 ºC. In most cases the pH values will not be off by more than ± 0.02 pH even at 37 ºC and at molarities slightly different from those given (usually 0.05 M). The methods of preparation described are not necessarily identical with those of the original authors. The titration curves of the majority of the buffers recommended have been redetermined by the writer. The buffers are arranged in the order of ascending pH range. 1. Hydrochloric Acid-Potassium Chloride Buffer. Stocks solutions A: 0.2 M solution of KCl (14.91 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 97.0 78.0 64.5 51.0 41.5 33.3 26.3 20.6 16.6 13.2 10.6 8.4 6.7 jun 14, 2004 pH 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 Pag.1 2. Glycine-HCl Buffer. Stocks solutions A: 0.2 M solution of glycine (15.01 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 5.0 6.4 8.2 11.4 pH 3.6 3.4 3.2 3.0 x 16.8 24.2 32.4 44.0 pH 2.8 2.6 2.4 2.2 3. Phthalate-Hydrochloric Acid Buffer. Stocks solutions A: 0.2 M solution of potassium acid phthalate (40.48 g in 1 L) B: 0.2 M HCl 50 mL of A + x mL of B, diluted to a total of 200 mL x 46.7 39.6 33.0 26.4 20.3 pH 2.2 2.4 2.6 2.8 3.0 x 14.7 9.9 6.0 2.63 pH 3.2 3.4 3.6 3.8 4. Aconitate Buffer. Stocks solutions...
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...the log of the ratio of conjugate base to conjugate acid. This proves the Henderson Hasselbalch equation. b. The addition of a strong acid would decrease the pH, since water is a neutral solution. It has nothing to account for the increase of H+ ions. The addition of a strong acid to the buffer, however, would generally not affect the pH. The buffer has a conjugate base which would be able to accept the excess of H+ ions, therefore not greatly effecting the pH. H3O+ would form, which would then react with A- to form HA and H2O. c. Diluting the acid would overall increase the pH of the solution. The dilution would cause an increase in volume, while the moles of H+ ions remains the same, therefore decreasing the concentration of H+ ions. If sufficiently diluted, the solution would become neutral with a pH of 7. d. The pH value of our most diluted buffer sample compared to our undiluted sample were not as similar as we would have expected. We believe that the difference in pH’s is due to the minimal time allowed for the undiluted buffer to reach equilibrium before having the pH measured. In addition to this, our pH meter was malfunctioning and had to be zero’d several times throughout the lab. The difference between the first and second dilutions was more appropriate for a buffer, showing...
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