Potentiometry MCQ Quiz Questions And Answers

The hydrogen electrode is considered the standard electrode in potentiometry because it has a well-defined and reproducible potential. It is used as a reference electrode to measure the potential of other electrodes in a solution. The standard hydrogen electrode consists of a platinum electrode immersed in a solution of 1 M HCl, with hydrogen gas bubbling through it. The potential of the hydrogen electrode is defined as 0 volts at all temperatures, making it an ideal reference point for measuring electrode potentials.

Potentiometry is the correct answer because ion selective electrodes measure the potential difference across a membrane. Potentiometry is a technique that measures the potential difference between two electrodes, which in this case are the ion selective electrode and a reference electrode. This potential difference is proportional to the concentration of the specific ion being measured. Coulometry measures the quantity of electricity transferred during an electrochemical reaction, amperometry measures the current flowing in an electrochemical cell, and conductivity measures the ability of a solution to conduct an electric current.

In an electrolytic cell, reduction takes place at the cathode. The cathode is the electrode where positively charged ions are attracted and gain electrons, leading to a reduction reaction. This is in contrast to the anode, where oxidation occurs and electrons are lost. The combination electrode is a type of electrode that combines both the anode and cathode in one unit, allowing for both oxidation and reduction reactions to occur. The electrode response refers to the overall behavior and characteristics of the electrode in the cell.

The correct answer is saturated KCl because the glass electrode of a pH meter requires a stable and conductive electrolyte solution. Saturated KCl solution is commonly used as it provides a stable reference potential and minimizes the effects of potential changes due to temperature or other factors. It also helps maintain a constant ionic strength and prevents the electrode from drying out. Concentrated HCl, dilute KCl, and dilute HCl are not suitable choices as they may affect the stability and accuracy of the pH measurement.

Potentiometry is the measurement of the voltage difference between two half-cells immersed in a solution. It is a technique used to determine the concentration or activity of ions in a solution by measuring the potential difference between an indicator electrode and a reference electrode. This method is commonly used in analytical chemistry to study electrochemical reactions and determine the equilibrium constants of redox reactions.

An indicator electrode is a type of electrode that represents the potential changes in an ion species that is present in the solution in which it is immersed. This electrode is used to determine the concentration of a specific ion in a solution by measuring the potential difference between the indicator electrode and a reference electrode. It is commonly used in analytical chemistry to monitor pH levels or to detect the presence of certain ions in a solution.

The description of mercury covered by a layer of mercurous chloride in contact with saturated potassium chloride solution matches the characteristics of a calomel electrode. Calomel electrodes are commonly used in electrochemical measurements and are made up of a mercury electrode covered by a layer of mercurous chloride (Hg2Cl2) in contact with a saturated potassium chloride (KCl) solution. This electrode is often used as a reference electrode due to its stable and reproducible potential.

If the viscosity of the support medium used in a protein electrophoresis system is too high, it means that the medium is thick and resistant to flow. In this case, the migration of proteins through the medium will be hindered and slowed down, resulting in a decrease in migration. Therefore, the correct answer is decrease.

The correct answer is CO2 + H20 ----> H2CO3 ----> H+ + HCO3. In this reaction, carbon dioxide (CO2) reacts with water (H2O) to form carbonic acid (H2CO3). Carbonic acid then dissociates into hydrogen ions (H+) and bicarbonate ions (HCO3-). This reaction results in a change in pH because the formation of hydrogen ions increases the acidity of the solution.

Selectivity refers to the ability of an indicator electrode to respond specifically to a single species of ion and not any other. In other words, it measures the electrode's ability to discriminate between different ions and only respond to the one it is designed for. Sensitivity, on the other hand, refers to the electrode's ability to detect and respond to small changes in concentration, while accuracy and precision refer to the electrode's ability to provide measurements that are close to the true value and consistent, respectively.

The correct answer is Ecell = Ecathode + Elj - Eanode. This formula is used to calculate the electromotive force (EMF) of a sample cell. The EMF is determined by the difference in potential between the cathode and the anode, with the contribution of the liquid junction potential (Elj) added. This formula takes into account the direction of electron flow and the potential differences at each electrode.

The incorporation of di-p-octylphenyl phosphate into a polyvinyl chloride membrane allows for the manufacture of an ion-selective electrode that is highly selective for calcium. Di-p-octylphenyl phosphate acts as a calcium ionophore, which means it selectively binds to calcium ions and allows them to pass through the membrane. This selectivity is important for accurate measurement of calcium levels in various applications, such as clinical diagnostics or environmental monitoring.

The pCO2 electrode is used to measure the partial pressure of carbon dioxide in a solution. It works based on the principle of potentiometry, where a potential difference is generated between the reference electrode and the working electrode. This potential difference is proportional to the pCO2 concentration. Therefore, the statement "Measurement is amperometric" is not associated with a pCO2 electrode because it is a potentiometric measurement.

Electrodes made of pH sensitive glass are used in the analysis of PCO2, PO2, and pH. These electrodes are designed to measure the concentration of hydrogen ions in a solution, which is directly related to the pH level. By measuring the pH level, these electrodes can provide information about the partial pressure of carbon dioxide (PCO2), the partial pressure of oxygen (PO2), and the overall pH of a solution. Therefore, both options (a) and (c) are correct as they include the analysis of PCO2 and pH.

Silver/silver chloride is used both as an internal reference element in potentiometric ion-specific electrodes and as an external reference electrode half-cell of constant potential required to complete a potentiometric cell. It provides a stable and reproducible reference potential, making it suitable for use in potentiometric measurements. Calomel, mercury vapor, and platinum are not commonly used as reference electrodes in this context.

In order for a Nernst equilibrium potential to exist for a given charged ion species across a semipermeable membrane, there must be a concentration gradient for that ion species across the membrane. This means that there must be a difference in the concentration of the ion on either side of the membrane. This concentration gradient is what drives the movement of the ion across the membrane, eventually leading to the establishment of an equilibrium potential. The other conditions mentioned in the question, such as the membrane being permeable to multiple ion species or the membrane potential constantly changing, are not necessary for the existence of a Nernst equilibrium potential.

The correct answer states that the net charge of the proteins in a sample is directly proportional to electrophoretic mobility. This means that as the charge of the proteins increases, their mobility during electrophoresis also increases. This relationship makes sense because proteins with higher charges will experience stronger attractions or repulsions from the electric field, causing them to move faster or slower, respectively. Therefore, the more charged a protein is, the greater its electrophoretic mobility will be.

The reference potential of a silver-silver chloride electrode is determined by the concentration of potassium chloride filling solution. This is because the electrode relies on the redox reaction between silver and silver chloride, which is facilitated by the presence of chloride ions. The concentration of potassium chloride in the filling solution affects the concentration of chloride ions available for the reaction, thus influencing the reference potential of the electrode.

One osmol of a substance is equal to the gram molecular weight divided by the number of particles or ions into which the substance dissociates in solution. This is because an osmol is a unit of measurement for the number of particles or ions in a solution, and it is defined as the amount of a substance that will react with or be replaced by one mole of electrons during a chemical reaction. Therefore, to calculate the number of osmoles, we need to divide the gram molecular weight by the number of particles or ions.

Combination electrodes refer to a type of electrode where the testing electrode and reference electrode are contained within a single unit. This means that both electrodes are combined into one device, making it more convenient and efficient for measurements. The use of a combination electrode eliminates the need for separate electrodes and simplifies the measurement process. The calomel electrode mentioned in the question is an example of a combination electrode.

Immunofixation electrophoresis involves exposing electrophoresed proteins to antisera against different immunoglobulin heavy and light chains, which leads to the precipitation of the proteins. This technique helps in identifying and characterizing specific immunoglobulins present in a sample. By observing the resulting precipitation pattern, it is possible to determine the presence and quantity of different immunoglobulins, which can be useful in diagnosing and monitoring various diseases, such as multiple myeloma and other plasma cell disorders.

A PCO2 electrode is a potentiometric cell in which carbon dioxide gas from the sample diffuses through a membrane and forms carbonic acid. Potentiometric cells measure the potential difference between two electrodes, in this case, the PCO2 electrode and a reference electrode, to determine the concentration of a specific ion or gas. In this case, the PCO2 electrode measures the concentration of carbon dioxide in a sample by allowing the gas to diffuse through a membrane and react with water to form carbonic acid. The potential difference generated by this reaction is then measured to determine the concentration of CO2.

Valinomycin is a neutral antibiotic that has a high affinity for potassium ions. When incorporated into a polyvinyl chloride membrane, it allows for the manufacture of an ion-selective electrode that is highly selective for potassium. This means that the electrode will primarily detect and measure potassium ions in a solution, making it useful for potassium ion analysis in various applications.

When an electrophoretic buffer is diluted before use, it means that the concentration of ions in the buffer is reduced. This would result in a decrease in the electrical resistance of the buffer. As a consequence, the electric field strength would increase, leading to an increased migration rate of proteins during electrophoresis. Therefore, the correct answer is "Increased migration rate of protein".

The likely cause for the distorted and large appearance of the albumin band on a serum protein electrophoresis is sample overload. This means that too much of the sample was loaded onto the gel, causing overcrowding and smearing of the bands.

Proteins migrate in an electric field based on their charge. The anode is positively charged, so proteins with a negative charge will migrate towards it. In this case, Protein C has an isoelectric pH of 8.6, which is higher than the electrophoretic buffer pH of 8.6. This means that Protein C will have a negative charge and will migrate towards the anode. Protein A has an isoelectric pH of 7.2, which is lower than the buffer pH, so it will have a positive charge and migrate towards the cathode. Protein B has an isoelectric pH of 5.1, which is also lower than the buffer pH, so it will have a positive charge and migrate towards the cathode as well. Therefore, the correct order of mobility from slowest to fastest towards the anode is C, A, B.

Coulometry is an electrochemical technique that is used to measure the concentration of chloride in serum or plasma. It works by passing a known electric current through the sample and measuring the amount of charge required to oxidize the chloride ions present. This method is highly accurate and precise, making it a commonly used technique in clinical laboratories for measuring chloride levels. The Guthrie test is a different test used for detecting phenylketonuria, and amperometry and voltammetry are also electrochemical techniques but are not specifically used for measuring chloride levels.

A and D are correct. A pH electrode monitors changes in H+ concentration, and a glass electrode containing silicon dioxide, sodium, and aluminum oxide is useful for monitoring changes in the concentrations of the blood gases oxygen and carbon dioxide. 

When a solute is added to a solvent, it lowers the freezing point, raises the boiling point, and raises the osmotic pressure of the solution. However, it does not raise the vapor pressure. In fact, adding a solute to a solvent lowers the vapor pressure of the solution compared to the pure solvent. This is known as Raoult's Law. Therefore, the correct answer is "Raise vapor pressure by 0.3 mmHg."

The correct answer is Calomel. Calomel is commonly used as a reference electrode in pH measurements because it has a stable and reproducible potential. It consists of a mercury-based electrode with a calomel paste that acts as a reference electrolyte. The calomel electrode is widely used in various industries and scientific research due to its reliability and accuracy in pH measurements.

The freezing point osmometer differs from the vapor pressure osmometer in that it is sensitive to ethanol. This means that the freezing point osmometer can accurately measure the osmolality of a solution containing ethanol, whereas the vapor pressure osmometer may not be able to do so. The other options mentioned in the question (cooling the sample, requiring a thermoelectric module, and requiring calibrations with aqueous standards) are not specific to the freezing point osmometer and may apply to both types of osmometers.

Amperometry is the correct answer because it involves monitoring the current at an electrolytic electrochemical cell that is generated at a fixed voltage and is proportional to the concentration of analyte present in the test sample in solution. This technique is commonly used in electrochemical analysis to measure the concentration of various substances. Coulometry, potentiometry, and osmometry are different techniques that are not specifically related to monitoring current in an electrolytic cell.

Ion-selective analyzers using undiluted serum samples have an advantage over analyzers that use diluted samples because they are not subject to pseudohyponatremia caused by high lipids or high proteins. Pseudohyponatremia is a condition where the sodium levels appear lower than they actually are due to interference from substances like lipids or proteins in the sample. By using undiluted samples, the ion-selective analyzers can accurately measure the concentration of ions without being affected by these substances, providing more reliable results.

The correct answer is "Polymer membrane". This type of ion-selective electrode uses a polymer membrane as the sensing element. The polymer membrane is designed to selectively allow certain ions to pass through, while blocking others. This allows the electrode to measure the concentration of specific ions in a solution. Polymer membrane electrodes are commonly used in various applications, including environmental monitoring, medical diagnostics, and industrial processes.

The observed freezing point of an aqueous solution is directly related to its molality. In this case, the observed freezing point is -0.93, which means that the molality of the solution is 500.

The total protein concentration in the sample is 85 g/dL, and 55% of this value represents the albumin concentration. 55% of 85 g/dL is 46.8 g/dL.

Coulometry is the technique used to determine the absolute amount of electroactive substance by measuring the amount of current passing between two electrodes in an electrochemical cell during a titration reaction. It involves the quantitative measurement of electric charge and is often used in the analysis of metals and other electroactive substances. Amperometry measures the current at a constant potential, potentiometry measures the potential difference between two electrodes, and turbidimetry measures the scattering of light to determine the concentration of particles in a solution.

In serum protein electrophoresis, proteins migrate towards the anode based on their charge and size. IgD, being the smallest protein, migrates the fastest towards the anode. Fibrinogen, being larger than IgD, migrates next. Transferrin, being smaller than Haptoglobin and Albumin, migrates before them. Haptoglobin, being larger than Transferrin and Albumin, migrates before Albumin. Therefore, the correct order of migration towards the anode is IgD, Fibrinogen, Transferrin, Haptoglobin, Albumin.

The weight of 1 osmol of NaCl is 29 grams.

Hemolysis refers to the breakdown of red blood cells, resulting in the release of their contents into the surrounding fluid. In protein electrophoresis using agarose gel, the different protein fractions are separated based on their size and charge. Hemolysis can affect the banding pattern by causing a decrease in the alpha2-globulin band. This is because hemolysis leads to the release of hemoglobin, which is a protein that primarily falls within the alpha2-globulin fraction. Therefore, the presence of hemoglobin in the specimen would result in a decrease in the alpha2-globulin band.