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What is elastic deformation? | The non-permanent deformation, that is, it is completely recovered when the applied stress ceases. | Permanent deformation, that is, that it does not fully recover when the applied stress ceases. | Deformation in the case of polymeric materials. | Chemistry | The partially permanent deformation, which partially recovers when the applied stress ceases. | 29 | 2 | 0136a4ad-8405-47dd-bebd-9d7e958a09a8 | 2022 |
The molecule CS2 belongs to the point group: | Cs. | C2V. | D∞h. | Chemistry | C∞v. | 30 | 4 | c0fce2b6-7f78-446f-aebe-e60df8afe4e1 | 2022 |
Both Zn2+ and Cu1+ ions are coordinated by cysteine thiolates in living systems. What is the geometry of these coordination compounds? | Tetrahedral for Zn2+ and linear for Cu1+. | Square-planar for both metals. | Tetrahedral for both metals. | Chemistry | Tetrahedral for Cu1+ and linear for Zn2+. | 31 | 2 | bc840f69-01c8-49fc-9050-28d260ab7f4e | 2022 |
What product is obtained in the direct reaction of hydrogen, H2, with alkali metals, M? | MHx, 0.5<x<0.7. | MH. | M5H. | Chemistry | MH2. | 32 | 1 | a20cc949-9f74-4f47-b879-cec1ab203753 | 2022 |
Indicate, among the following nuclides, which one is expected to lack radioactive activity: | 82As (Z = 33). | 57Cu (Z = 29). | 208At (Z = 85). | Chemistry | 114Sn (Z = 50). | 33 | 3 | 140dc8ab-67ee-4d8e-9bdd-6b1dba326b76 | 2022 |
Some ligands can bind in different ways to the central metal ion of a complex ion. For example, the nitrite ion, a monodentate ligand, has pairs of electrons available for coordination both on the N atoms, and on the O. This type of behavior gives rise to: | Bond or linkage isomerism. | Coordination isomerism. | Ionization isomerism. | Chemistry | Isomerism of donor atom. | 34 | 2 | 9429691f-64fa-41f2-b8b8-123be3845aa3 | 2022 |
Which structural concept is the Burgers vector associated with? | To the distortion associated with twinning. | To the distortion associated with dislocations. | To the distortion associated with inherent point defects. | Chemistry | To the distortion associated with specific point defects. | 35 | 1 | f4835ef9-a424-4aab-b6d4-54b3eb5ed9a4 | 2022 |
What is a semiconductor?: | Metallic material that has a full valence band at 0 K and a relatively narrow energy band. | Metallic material that has a full valence band at 0 K and a relatively wide energy band. | Non-metallic material that has a full valence band at 0 K and a relatively narrow energy band. | Chemistry | Non-metallic material that has a full valence band at 0 K and a relatively wide energy band. | 36 | 4 | 2f575aa4-900c-4cc4-bb52-04ad5f61c096 | 2022 |
One of the following propositions about dinitrogen monoxide is uncertain or far from its chemical behavior: | It can be used as a propellant gas in pressurized cans of products such as cream. | It can be used as a laughing gas and/or anesthetic. | It can be used to increase the power of combustion engines. | Chemistry | It is a very stable gas at any temperature. | 37 | 3 | 333ca043-0020-4ef5-a764-4adacf6ca55a | 2022 |
The 𝟖𝟒Po 𝟐𝟏𝟎 spontaneously decays to 𝟖𝟖pb 𝟐𝟎𝟔 with emission of: | A β particle. | An α particle. | A proton. | Chemistry | A positron. | 38 | 1 | bc4cf548-44c3-4e98-8c7a-a18b2759d77b | 2022 |
What is the function of the small ligands called siderophores in organisms? | Help the consumption of iron by organisms, by forming a soluble complex of Fe3+. | Assist in the storage of iron by organisms, by forming an insoluble complex of Fe3+. | Help in the transformation of the Fe3+ ion into atomic Fe. | Chemistry | Assist in the transport of ionic iron, in the form of Fe2+, from the inside to the outside of the cells. | 39 | 2 | d6731dad-47e2-4be3-b0f1-7b16d3317a9a | 2022 |
If cyanogen (CN)2 is bubbled through a basic solution, it is expected that, as a result, the following aqueous ionic species would form: | Cyanate. | Cyanide and cyanate. | Carbonate and nitrite. | Chemistry | Cyanide. | 40 | 1 | 31824f2f-e03b-4b76-b66a-141e49eedcfa | 2022 |
The triple point of water is at a pressure of 4.58 mm of Hg and a temperature of +0.01ºC. A certain amount of water at -50.0ºC is heated to 120ºC at a constant pressure of 4.40 mm of Hg. The phase transitions that occur in this process are: | Liquid → Gas. | Solid → Liquid → Gas. | Solid → Gas. | Chemistry | Solid → Liquid. | 41 | 4 | 21922543-d6df-4a61-a8cc-0571b4daec82 | 2022 |
Which of the following statements is true?: | A chemical reaction whose activation energy is equal to zero is instantaneous. | In a chemical reaction with a high activation energy, the rate constant strongly depends on the temperature. | The rate constant of a chemical reaction does not depend on the activation energy. | Chemistry | A chemical reaction with a negative activation energy cannot occur. | 42 | 1 | ff057086-7b8d-4616-a05f-e52ad907393e | 2022 |
Most industrial chemical reactions take place in the presence of solid catalysts. For a solid catalyst to be effective, one or more of the reactants must be chemisorbed on the solid catalyst. Indicate the incorrect sentence: | A good catalyst should have moderate values of the enthalpy of adsorption with the reactants. | Physical adsorption is only important in some special cases, such as in the recombination of radicals. | Small amounts of certain substances that strongly bind to the catalyst can deactivate or poison it. | Chemistry | The conversion rate of a catalytic reaction has units of mol∙s-1∙m-3. | 43 | 3 | 581da089-8ec9-4a50-a78e-f20570e6d515 | 2022 |
Which statement is correct in relation to the molar conductivity of weak electrolytes in aqueous solution?: | The molar conductivity of weak electrolytes does not depend on their concentration. | The molar conductivity of weak electrolytes slightly decreases as the square root of their concentration increases. | The molar conductivity of a weak electrolyte at a certain concentration allows to determine its degree of dissociation if its limit molar conductivity is known. | Chemistry | Unlike for strong electrolytes, the molar conductivity of weak electrolytes does not depend on temperature. | 44 | 4 | 9d3e1c4c-e05c-4b50-afd2-9a3a6a8e3686 | 2022 |
If heat is applied to melt the pentahydrate sodium thiosulfate salt (Na2S2O3∙5H2O(s)): | The reverse process is exothermic. | The process is exothermic. | The enthalpy change of the process is less than zero. | Chemistry | The reverse process is endothermic. | 45 | 2 | c454335c-654f-4050-8611-607ca87db4f7 | 2022 |
The activity of a real solute A in a solution is equal to: | The partial pressure of A in the solution divided by the vapor pressure of the pure component. | The product of the partial pressure of A in the solution by Henry's constant. | The product of the partial pressure of A in the solution by the vapor pressure of the pure component. | Chemistry | The partial pressure of A in the solution divided by Henry's constant. | 46 | 3 | f79f3d9d-26e6-4189-ba4a-55d63b2ad2e7 | 2022 |
When a liquid wets a tissue, it is due to a phenomenon called capillary rise. Capillary rise occurs when inserting a capillary tube into a liquid, and measuring the height allows understanding the surface tension between the liquid and the air. Indicate the incorrect statement: | The surface tension has units of J∙m-2. | The surface tension has units of N·m-1. | The water-air interface is a convex curve. | Chemistry | The water-air interface is a concave curve. | 47 | 4 | 2e22a8ad-b618-4959-8d8a-f607afbc08d8 | 2022 |
A second-order rate constant can be written with units of: | L∙ mol-1∙ s-1. | s-1. | Mol2∙ L-2∙ s-1. | Chemistry | Mol∙ L-1∙ s-1. | 48 | 2 | a341ddff-bea2-4516-b3fe-4f36051c2822 | 2022 |
The latent heat of fusion of a substance is equal to its: | Latent heat of condensation. | Latent heat of solidification. | Latent heat of sublimation plus its latent heat of vaporization. | Chemistry | Latent heat of sublimation minus its latent heat of vaporization. | 49 | 3 | b9784e9e-03d8-458e-8ffb-3991171f3046 | 2022 |
In 1836, Edmund Davy, dissolving potassium carbide in water, obtained a hydrocarbon that he named klumeno, which would be renamed 24 years later by P.E.M. Berthelot as acetylene. This hydrocarbon is the only one soluble in water. This fact is justified because acetylene: | It presents dipoles in the C-H bonds. | Floats in the water. | Forms hydrogen bridges with water. | Chemistry | It has an ionic bond. | 50 | 2 | 473b46a1-dcc1-4fd6-b2df-413531d22038 | 2022 |
If we ask for 96º alcohol in a pharmacy, they are selling us: | An azeotropic mixture of 96% alcohol and 4% water with a boiling point between the boiling point of water and the boiling point of alcohol. | Pure alcohol. | An azeotropic mixture of 96% alcohol and 4% water with a boiling point lower than the boiling point of water and the boiling point of alcohol. | Chemistry | Alcohol whose boiling point is 96ºC. | 51 | 4 | bd4aee7e-3564-4f5b-adb2-e85e272a2d79 | 2022 |
What does Pauli's exclusion principle state? | When the coordinates of two fermions are swapped in a wave function, the sign of the wave function changes. | In hydrogenoid atoms, it is not allowed for two or more electrons to have identical quantum numbers. | The ground state configuration of a poly-electronic atom is the one that has the highest number of unpaired electrons. | Chemistry | The maximum capacity of an orbital of a poly-electronic atom depends on its atomic number. | 52 | 2 | d6e1a9a8-aa13-440d-a54b-6590ae93b4a0 | 2022 |
Which of the following pairs of molecules have the same hybridization in the central atom? (The central atom is underlined): | H2O, HNO. | HOCl, ClF3. | BeH2, NH3. | Chemistry | HCN, CO2. | 53 | 3 | 26b32bbf-bf48-485f-8cca-5f831661349b | 2022 |
Which of the following species has the longest bond?: | CN. | CN+. | The three species have the same bond length. | Chemistry | CN-. | 54 | 1 | 621132b9-faff-4484-90b2-161d17db5d9f | 2022 |
What is a hydrogen bond?: | A covalent bond between a hydrogen atom and an electronegative atom. | An interaction between ions. | An interaction between an electronegative atom of one molecule and a hydrogen atom bonded to an electronegative atom of another molecule. | Chemistry | A type of bond between proteins and lipids that are part of biological membranes. | 55 | 4 | 280988b0-dbe2-45f5-85df-601206c97ff6 | 2022 |
At the azeotropic point of a solution of two totally miscible liquids: | The concentration of the most volatile component in the liquid phase is higher than in the vapor phase. | The concentration of the most volatile component in the liquid phase is the same as in the vapor phase. | The concentration of the less volatile component in the liquid phase is lower than in the vapor phase. | Chemistry | The concentration of the most volatile component in the liquid phase is lower than in the vapor phase. | 56 | 1 | 7548645c-1066-4e93-82ba-8027d6a2aa0f | 2022 |
What effect is observed when glycerin is added to a liter of water? | The temperature of the water increases. | Water evaporates more easily. | Decreases the viscosity of water. | Chemistry | Decreases the freezing point of water. | 57 | 3 | 14a81316-e53a-4c05-bda6-06e1b74b166b | 2022 |
Which of the following species is paramagnetic?: | C2. | B2. | CO. | Chemistry | N2. | 58 | 1 | 8afce931-95e2-4d1c-b882-4c032388dfc6 | 2022 |
In the vaporization equilibrium, an increase in pressure leads to the following effect on the boiling temperature: | The boiling temperature increases if the pressure increases. | The boiling temperature does not vary with pressure. | Just increase the pressure. | Chemistry | The boiling temperature decreases if the pressure increases. | 59 | 2 | 0f79763d-13a0-4043-98f1-1de11fd8c2da | 2022 |
Which of the following substances will have a lower critical micellar concentration (CMC) value?: | C9H19SO3Na. | C6H13COOK. | C8H17COONa. | Chemistry | C11H23NH4Cl. | 60 | 3 | dd3943dd-ceeb-4e21-be93-8990e80cc7eb | 2022 |
For a chemical reaction that takes place in a galvanic cell whose normal electromotive force (E0) varies positively with temperature: | The change in molar entropy in the normal state is equal to zero. | The change in molar entropy in the normal state is greater than zero. | Energy is released in the form of heat. | Chemistry | The change in molar entropy in the normal state is less than zero. | 61 | 1 | 2f3aead0-b86d-41c2-ad53-eceae9a400ff | 2022 |
A sample of gas is present in a volume V1 at a pressure P1 and temperature T1. When the temperature changes to T2, keeping the volume constant, the pressure P2 will be: | P1T17T2. | P1/T1T2. | P1T2/T1. | Chemistry | T1/P1T2. | 62 | 4 | abc42a08-02f8-40ab-8eb4-d6854c164545 | 2022 |
What is an anti-bonding molecular orbital? | It is an orbital with cylindrical symmetry around the bond between two atoms. | It is an orbital that, if occupied, reduces the bond strength between two atoms. | It is an orbital that is mostly located far from the bonding line between two atoms. | Chemistry | It is an orbital in which one of the atoms has a much greater contribution than the other. | 63 | 1 | fdcccee4-e0e0-4705-93ff-5b87c80ee38e | 2022 |
A substance has a heat of condensation of -1.46 kJ g-1 and a heat of sublimation of 4.60 kJ g-1, what is the heat of solidification, in kJ g-1? | -6.06. | 3.14. | 6.06. | Chemistry | -3.14. | 64 | 3 | 37669fba-7b98-4d2f-9d02-c7281f92d555 | 2022 |
In what units is the electrical conductivity, к of an electrolyte solution measured? | Ohms m-1. | Ohms m. | Ohms-1 m. | Chemistry | Ohms-1 m-1. | 66 | 3 | bf042196-1377-471d-90f6-e5c8321a85a2 | 2022 |
Given the following molecules, what is the correct decreasing order of their bond angles?: | BCl3 > CCl4 > BeCl2 > NCl3 > Cl2O. | BeCl2 > BCl3 > CCl4 > NCl3 > Cl2O. | NCl3 > Cl2O > CCl4 > BCl3 > BeCl2. | Chemistry | BCl3 > CCl4 > NCl3 > Cl2O > BeCl2. | 67 | 1 | 64f014e2-0e91-4c22-b915-9ddb18b19a2a | 2022 |
Speaking of the symmetry of a molecule, what is a symmetry element? | An operation or movement that leaves the molecule indistinguishable from its initial state. | A property by which the molecule resembles others of its kind. | It is a point, line, or plane with respect to which a symmetry operation is performed. | Chemistry | A factor that determines the symmetry group to which a molecule belongs. | 68 | 4 | 41dcf011-cb80-4aa4-a502-cc29c1fc6939 | 2022 |
In a chemical reaction that follows a 2nd order kinetics, what units does the rate constant have? | M-1s-1. | M s-1. | s-1. | Chemistry | M-2s-1. | 69 | 2 | fc3423b3-dd36-4868-8bcb-b1eaa1243eb1 | 2022 |
Two gaseous systems that can exchange energy both in the form of heat and work with each other and isolated from the outside reach equilibrium when: | The entropies of both systems are equal. | The internal energies of both systems are equal. | The volumes of both systems are equal. | Chemistry | The temperatures and pressures of both systems are equal. | 70 | 3 | 41abc2ac-eb64-4f6e-8a1e-a74ace584515 | 2022 |
In which of the following reactions is the first reactant the oxidizing agent: | NaOH + HNO3 → NaNO3 + H2O. | Fe + Pb(NO3)2 → Fe(NO3)2 + Pb. | CO2 + C → CO. | Chemistry | H2 + CuO → H2O + Cu. | 71 | 4 | a0510cb0-8117-42c4-aac8-e826dc9d48a0 | 2022 |
Which of the following combinations of liquids would be expected to have a higher vapor pressure than what would be predicted by Raoult's law?: | Acetone and water. | Ethanol and hexane. | Nitric acid and water. | Chemistry | Isopropanol and methanol. | 72 | 1 | 518008ad-9172-46b2-a6dd-acf8eca4160c | 2022 |
What type of species can the steady-state approximation be applied to in a kinetic study? | To substances that participate in very slow reactions. | To substances that participate in very rapid reactions. | To species that participate in the determining stage of the reaction speed. | Chemistry | To intermediate species whose concentration remains close to a constant value. | 73 | 3 | cda21228-a3c7-41a5-bea9-e56b344f1157 | 2022 |
Hydrogen gas is compressed at a constant pressure of 10 atm, at 50ºC. The observed volume change is 10L. The work done, in joules, is: | -1.0∙102 J. | -1.0∙104 J. | 1.0∙104 J. | Chemistry | 1.0∙102 J. | 75 | 4 | a6a9f9e2-5cec-41be-8d33-54e3d7ee85bd | 2022 |
The following chemical reaction takes place in a galvanic cell: Pb(s) + Cu(no3)2(aq) → Pb(no3)2(aq) + Cu(s). The abbreviated notation that represents the reaction is: | Cu(s) I Cu2+ (aq) II Pb2+ (aq) I Pb(s). | Pb(s) I Pb2+ (aq) II Cu2+ (aq) I Cu(s). | Cu(s) I Cu(NO3)2(aq) II Pb(NO3)2(aq) I Pb(s). | Chemistry | Pb(s) I NO3 -(aq) II NO3-(aq) I Cu(s). | 76 | 1 | dafe9d6b-2a57-479b-bb82-7e829c81c1b4 | 2022 |
Considering that the liquid + gas ⇌ solution process is exothermic, explain why cava is served in cold glasses: | Its molar volume is larger at lower temperatures, and therefore more services can be performed when the cup is cold, with the consequent economic gain. | It would change color when heated. | When the glass is cold, any potential "heating" is delayed, as this way it goes less to the head. | Chemistry | It rapidly degasses if poured into a hot glass. | 77 | 3 | 04a6aa8d-cb28-43bb-90b2-ee675b95d4c6 | 2022 |
CO2 cannot be liquefied by increasing the pressure at temperatures above 31ºC, what is this temperature called?: | Triple point temperature. | Liquefaction temperature. | Liquid transition temperature. | Chemistry | Critical temperature. | 78 | 3 | 7f3b700c-9dfb-4c4a-8330-fbf956353403 | 2022 |
Hund's rule of maximum multiplicity states: | In an atom, there cannot be two electrons with all the quantum numbers being the same. | An orbital cannot be occupied by more than two electrons, and when two electrons occupy the same orbital, their electrons cannot be paired. | An atom in its ground state adopts the configuration with the largest number of unpaired electrons. | Chemistry | An orbital cannot be occupied by more than two electrons, and when two electrons occupy the same orbital, their electrons must be paired. | 79 | 4 | cc3da2fc-ffd4-4af4-82ba-ccb26a4b38fa | 2022 |
Why do deviations from the ideality of a gas occur? | At the pressure. | At the temperature. | To the expansion. | Chemistry | To the intermolecular forces. | 80 | 3 | b6dd7e62-e983-4f6c-8cbe-243dd5be50f9 | 2022 |
In a dilute aqueous solution of potassium sulfite, it is found that: | 2 ∙[K+] = [HSO3-]. | [H+] + [K+] = [OH-] + [HSO3-] + [SO32-]. | [K+] = [SO32-]2. | Chemistry | [K+] = 2∙([ H2SO3-] + [HSO3-] + [SO32-]). | 81 | 3 | ce04ef7f-55ab-4435-b6ed-9f189b4dd9bb | 2022 |
In the technique of high-performance liquid chromatography (HPLC), the isocratic elution mode is one in which: | A mobile phase is used whose composition changes during the separation. | The temperature of the mobile phase changes during the separation. | A mobile phase is used whose composition remains constant during the separation. | Chemistry | The flow rate of the mobile phase changes during the separation. | 82 | 4 | 371d8087-3046-4e43-bea0-58c83dd7ec5d | 2022 |
In which of the following media is SrCO3 more soluble?: Data: Sr2+ does not present parasitic reactions at any pH value. Acid constants H2CO3: pKa1=6.4; pKa2=10.3. | In a buffer solution whose pH is 5. | In a buffer solution whose pH is 4. | In a buffer solution whose pH is 8. | Chemistry | In a buffer solution whose pH is 6. | 83 | 1 | 098318a9-e0ac-4273-9bcc-2d0e615eeb47 | 2022 |
How can microbial activity be reduced during the transport stage of a sample to the analysis laboratory? | Cooling the sample. | Heating the sample. | Using a container that protects the sample from light and air. | Chemistry | Adding a specific reagent. | 84 | 2 | 99aed881-6816-4f3c-8759-04a68e7a7e78 | 2022 |
What is the protonic balance of a NaHA solution? | [H3O+] + [A2-] = 2[H2A] + [OH-]. | [HA-] = [H3O+] + [A2-] + [HO-]. | [H3O+] = [H2A] + 2[A2-] + [HA-]. | Chemistry | [H2A] + [H3O+] = [A2-] + [HO-]. | 85 | 3 | c332543a-7121-4eb9-aa9a-7001237da2b9 | 2022 |
Indicate the correct option in relation to the acidic or basic character of a species in solvents other than water: | In a solvent more basic than water, acids are stronger than in water. | In a solvent more basic than water, bases are stronger than in water. | The acid-base character of a species does not depend on the acid-base properties of the solvent in which it is found. | Chemistry | In a solvent more acidic than water, acids are stronger than in water. | 86 | 2 | cec8f13b-5e4d-4938-861d-ae5685e308c5 | 2022 |
The cholesterol concentration in 100 people is studied before and after administering a drug to reduce cholesterol concentration. What type of statistical test should be used to conclude about the efficacy of the administered drug? | F-test for comparing the precision of two groups of results. | T-test comparison of a sample mean with a reference value. | T-test for comparison of related or paired means. | Chemistry | T-test for comparison of the mean of two sets of independent results. | 87 | 4 | b0d45cd9-3cd4-48e0-afad-bde410acdab8 | 2022 |
What are the kinetic processes that contribute to peak broadening in chromatography? | Eddy diffusion, dead volume, mass transfer, and longitudinal diffusion. | Longitudinal diffusion, Eddy diffusion, mass transfer in the mobile phase and mass transfer to and from the stationary phase. | Mass transfer in the mobile phase and in the stationary phase, axial and radial molecular diffusion. | Chemistry | Axial molecular diffusion, radial mass diffusion and Eddy diffusion. | 88 | 1 | e1b2d97e-6d17-4e73-b8fe-8b97d6a02c7c | 2022 |
In a chromatographic separation, the resolution of a column constitutes a quantitative measure: | Of the degree of transfer of an analyte between the stationary and mobile phases. | Of the elapsed time from the injection of the sample until the peak concentration of the analyte reaches the detector. | Of the fraction of time that the analyte resides in the mobile phase. | Chemistry | On the capacity of the column to separate two analytes. | 89 | 3 | e4e69eac-7b40-4364-a50f-ea76caec573a | 2022 |
What is the pH of the solution obtained after adding 10 ml of 0.01 M HClO4 to 5 ml of 0.02 M NaOH? | 3. | 1. | 7. | Chemistry | 5. | 90 | 4 | cbad85aa-df3b-4b0a-959c-82ecbcc96538 | 2022 |
By representativeness of an analytical method, it is understood: | The degree of agreement between the results of a series of repeated measurements. | The degree of agreement between the value obtained in the measurement of a magnitude and the value that is considered real. | The property of an analysis method to provide a result consistent with the posed analytical problem. | Chemistry | The quality of an analytical method that measures its ability to resist small changes in operating conditions without its functioning being altered. | 91 | 4 | b54bfbc3-d834-4049-a365-43f6dd5f6bec | 2022 |
A widely used technique for protein separation is sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) with sodium dodecyl sulfate (SDS) as a denaturing agent. In this technique, proteins are separated based on the difference in: | Its molecular weight. | Their isoelectric points. | Its charge. | Chemistry | Its charge/radius ratio. | 92 | 2 | d61380f2-0e63-44f9-8701-784e00d10897 | 2022 |
In reference to nuclear magnetic resonance (NMR) spectroscopy: | It is used to study any atomic nucleus, although it has higher sensitivity for 1H. | It can only be used to study nuclei that contain an odd atomic number or atomic mass. | NMR cannot be used to study carbon, as its atomic number (Z) is 6. | Chemistry | In order to be analyzed by NMR, it is necessary for an atomic nucleus to have an odd number of protons. | 93 | 1 | 551795fe-6924-4e35-900a-127b89385068 | 2022 |
Which of the following factors favor molecular fluorescence?: | Presence of heavy atoms. | Increase in temperature. | Presence of dissolved oxygen. | Chemistry | Structural rigidity. | 94 | 3 | 09c711fd-e392-4941-8ce9-36d0edb81fad | 2022 |
What is the change in pH that occurs when diluting a buffer mixture consisting of 0.0500M NH3 and NH4Cl 0.0500M by 5 times? Data: pKb (NH3) = 4.8. | The pH increases by two units. | The pH increases by one unit. | The pH does not vary. | Chemistry | The pH decreases by one unit. | 95 | 4 | e678bb74-8ecc-4fd9-857c-e29691cbc480 | 2022 |
What happens in a reverse phase chromatographic separation when the polarity of the mobile phase increases? | That increases the retention time of the solutes. | That reduces the retention time of solutes. | That reduces the resolution time of the more polar solutes. | Chemistry | That increases the resolution of the column. | 96 | 2 | af558261-b4d3-4360-a001-40325fb37783 | 2022 |
Thermogravimetry or thermogravimetric analysis is a thermal analysis technique that is based on: | Record the difference in the enthalpy change between the sample and a reference material, when both are subjected to a controlled heating program to maintain them at the same temperature. | Record the mass of the sample as a function of temperature, or time while maintaining a constant temperature. | Measure the changes in the electrical conductivity of the sample based on the temperature. | Chemistry | Measure the evolution of some optical property of the sample as a function of temperature. | 97 | 1 | d4f0d925-b72b-49a7-87fd-51ac9c8700e8 | 2022 |
Copper (Cu) is to be quantified in human serum using inductive coupling plasma mass spectrometry (ICP-MS). Which of the following elements would be most suitable as an internal standard?: | Uranium. | Zinc. | Calcium. | Chemistry | Germanium. | 98 | 3 | b38dc701-32b5-444e-9d19-deb26c4aa0d9 | 2022 |
What type of ligand is ethylenediaminetetraacetic acid (EDTA)? | Tridentate. | Monodentate. | Hexadentate. | Chemistry | Tetradentate. | 100 | 4 | f3cffccf-2f18-473c-9c6b-ffeea99791bf | 2022 |
With 10 mL of a sample containing different anions (I-, Br-, Cl-, IO3-), all of them at a concentration of 0.0100 M, we carry out a titration with Agno3 0.0200 M, Kps (AgI) = 8.3∙10-17, Kps (AgBrO3) = 5.7∙10-5, Kps (AgBr) = 5.2∙10-13, Kps (AgCl) = 8.3∙10-10. Which will be the first precipitate to form? | AgBr. | Agl. | AgCl. | Chemistry | AgBrO3. | 101 | 1 | fc568402-5b7a-4fd9-9681-7e98e4b179b5 | 2022 |
To carry out the chromatographic separation of chiral compounds, you need: | A stationary phase formed by small particles linked with controlled pore size. | A stationary phase prepared by molecular imprinting of the two enantiomers. | A stationary phase in which an affinity ligand is immobilized on its surface. | Chemistry | A stationary phase with a chiral agent immobilized on its surface. | 102 | 3 | f9c99960-cf7a-4f26-bd6d-748c3f8e3b3f | 2022 |
What are isobaric interferences? | These are produced by elements that have isotopes whose mass is substantially the same. | These are produced in atomic emission spectroscopy due to the pressure of the plasma gases. | These are caused by poor nebulization of the sample. | Chemistry | These are produced by polyatomic species formed through interactions between plasma species and those of the sample matrix. | 103 | 2 | 8f547e75-5eaa-421c-9bc1-87be5896229e | 2022 |
In reverse phase or reserve chromatographic separations: | An ion exchange resin is used as the stationary phase. | Polar solutes are eluted more easily than non-polars. | Solvated molecules are separated exclusively according to their different sizes. | Chemistry | A stationary phase more polar than the mobile phase is used. | 104 | 1 | a3fd3a7d-26c5-4fe5-8260-d80551e6d3ab | 2022 |
In the titration of a weak monoprotic base (pKb = 5) with a strong acid, the pH at the equivalence point is: | pH = 7. | pH > 7. | pH = 5. | Chemistry | pH < 7. | 105 | 3 | d6850ddd-d2b2-4405-bd49-801b28131fe0 | 2022 |
When are back titrations recommended in complexometric titration? | When a metallochromic indicator is not available. | When a metallochromic indicator is available. | When the conditional constant of the EDTA does not depend on the pH. | Chemistry | When the conditional constant of EDTA depends on the pH. | 106 | 2 | 11e02961-7d3f-496e-93a9-b21db361509a | 2022 |
What is the limit of detection (LOD) of an analytical method? | The smallest analytical signal that can be differentiated from the background signal. | The slope of the calibration curve. | The concentration at which the calibration curve loses its linearity. | Chemistry | The proximity of a series of measurements from the same sample. | 107 | 2 | a23bbd09-08ae-4f9d-9b21-4797da018907 | 2022 |
Which of the following components belongs to a monochromator?: | Interference filter. | Absorption filter. | Diffraction grating. | Chemistry | Quadrupole. | 108 | 4 | 132e6417-4692-4e1e-b752-7c509d6431fa | 2022 |
Which of the following statements is correct for diagnostic tests?: | Both the positive predictive value (PPV) and the negative predictive value (NPV) depend on the prevalence of the disease in the studied population. | The higher the diagnostic sensitivity, the lower the percentage of false positive results. | The specificity of a test represents the probability that a sick subject will have a positive result in the test. | Chemistry | A very specific test offers a large proportion of false negative results. | 109 | 2 | fb60bbe6-683e-4744-bf2c-215919cca0bf | 2022 |
How does the potential of a redox system (Ox/Red) vary if a ligand L that forms complexes with the oxidized form is added? | The potential does not change. | The potential increases. | The potential becomes zero. | Chemistry | The potential decreases. | 110 | 3 | 08eb6e89-5097-4f83-b488-0e9cb3e40257 | 2022 |
If you want to improve the resolution in gas chromatography, you should use: | A column of larger caliber. | A longer column. | A carrier gas with a higher molecular weight. | Chemistry | A thicker stationary phase. | 111 | 1 | 97c68295-7a3a-4c45-aba2-b740cf7f8e72 | 2022 |
The separation technique called micellar electrokinetic capillary chromatography is a modality of: | Liquid partition chromatography that uses a solution containing micelles of a surfactant as the mobile phase. | Capillary gel electrophoresis. | High resolution liquid chromatography that uses a capillary column for separation. | Chemistry | Capillary electrophoresis that uses a separation buffer containing micelles of a surfactant. | 112 | 3 | ac31b4f0-14df-4c30-801e-cb779b6b139c | 2022 |
Which of the detectors used in gas chromatography has a universal response? | Of flame ionization. | Of electron capture. | Of thermal conductivity. | Chemistry | Of photoionization. | 113 | 4 | e68c1007-39ff-43db-b6dc-ffd47f89e98b | 2022 |
Which of the following statements is true?: | If pKa(HA) < pKa(HB), then A- is a stronger base than B-. | At any temperature, in aqueous solution it is satisfied that Kw = [H3O+] + [OH-]. | The acidity constant of an acid does not vary with temperature. | Chemistry | For a given acid-base pair, the highest buffering capacity occurs when their concentrations are equal. | 115 | 3 | f25b2e90-83b0-4cd3-a4cb-7ea0b7511ea4 | 2022 |
What is a quadrupole?: | An ion detector. | A mass analyzer. | Interface used in atomic mass spectrometry. | Chemistry | A radiation source used in the infrared region. | 116 | 1 | 4450fbf1-04e2-4352-b278-e0d8aeaeec1f | 2022 |
In a gas chromatography (GC) analysis, it is desired to accelerate the elution of the analytes, and thus shorten the analysis time. For this, it is recommended: | Use a more polar mobile phase. | Derivatize the samples to increase the volatility of the analytes. | Increase the oven temperature. | Chemistry | Use a more nonpolar mobile phase. | 117 | 4 | 6498615b-81b4-41a5-b948-6c127e262668 | 2022 |
Which of the following interferences is not found in immunoassays?: | Hook effect. | Cross-reactivity. | Interference by macrocomplexes. | Chemistry | Ionic Suppression. | 118 | 3 | 336d6040-f440-4261-afe9-b56359129e80 | 2022 |
In reverse phase liquid chromatography: | The less polar solvent has a stronger elution force. | The less polar solvent has less elution strength. | The elution strength does not depend on the polarity of the solvent, but on its ionic strength. | Chemistry | The elution strength of a solvent depends solely on the flow and pressure of the chromatography. | 119 | 2 | 851ca98c-8f46-4f49-8dd2-009374219576 | 2022 |
Which of the following factors is not a consequence of the partial hydrogenation of vegetable oils?: | Reduction of some double bonds in cis configuration to single bonds. | Increase in the risk of suffering from cardiovascular diseases for human consumers. | Reduction of the melting temperature. | Chemistry | Change of configuration from some cis double bonds to trans double bonds. | 121 | 4 | 7390ca47-2065-4ba8-82fb-964d71deb58a | 2022 |
Which of the following structural arrangements in a protein suggests that it is a DNA-binding regulatory protein: | Alpha Helix. | Zinc finger. | Disordered region. | Chemistry | Beta chain. | 122 | 1 | 9afd0575-c80d-421f-a3b2-b124747434c2 | 2022 |
The synthesis of urea requires the following enzymes, except: | Carbamoyl phosphate synthetase II. | Carbamyl phosphate synthetase I. | Argininosuccinate synthetase. | Chemistry | Ornithine transcarbamylase. | 123 | 2 | edb421fe-e500-47b2-b691-cc85dad3ea37 | 2022 |
Which of the following parameters rises more in the serum of a hemolyzed sample?: | Potassium. | Lactate dehydrogenase. | Calcium. | Chemistry | Inorganic phosphate. | 124 | 1 | 53ee69fd-18be-455b-8479-45686cfdb85a | 2022 |
Restriction endonucleases (or restriction enzymes): | They are used for the formation of hybrid molecules through recombination. | They hydrolyze phosphoester bonds starting from the 5' ends of the DNA. | They recognize and cut the DNA in specific recognition sequences. | Chemistry | They recognize and cut the DNA in nucleosome-free sequences. | 125 | 4 | 77940332-bdd9-4b7e-a6a8-792de8585199 | 2022 |
Which of the following statements about the complementarity of nitrogenous bases in DNA is true?: | The bases A and T are linked by 3 hydrogen bonds. | The bases G and C are joined by 3 hydrogen bonds. | The bases A and C are bound by 2 hydrogen bridges. | Chemistry | The bases A and G are joined by 2 hydrogen bonds. | 126 | 1 | 73cc5653-c074-41d2-9f47-a7c35de24a26 | 2022 |
Which of these statements referring to the chemiosmotic theory that relates mitochondrial electron transport and oxidative phosphorylation is correct?: | The energy released by electron transport is conserved as a transmembrane pH gradient. | The ATP synthase is not affected by the proton gradient. | Regardless of the entry point of the electrons in the transport chain, the number of ATP molecules synthesized is constant. | Chemistry | Oxidative phosphorylation can take place in a membrane-free system. | 127 | 2 | 21ed41a3-5f86-472c-a202-3bb7e8e8e314 | 2022 |
The main enzyme regulating the speed of the glycolytic pathway is: | Hexokinase. | Phosphofructokinase1. | Enolase. | Chemistry | Pyruvate dehydrogenase. | 128 | 1 | 97f6d0ca-74da-45f7-b8c5-24afa69d046f | 2022 |
What is the main use of glycosylated hemoglobin? | Diagnosis of diabetes mellitus. | Evaluate the metabolic control of a diabetic. | Indicate when gestational diabetes may occur. | Chemistry | Indicate when complications exist in diabetes. | 129 | 1 | 30b4bb2c-311b-4011-b489-60c2a241a02f | 2022 |
The brain is adapted to preferentially use glucose. Therefore, it can be expected that its glucose transporter would be: | Of low affinity and therefore with a high Km. | High affinity and therefore with high Km. | Of high affinity and therefore with low Km. | Chemistry | Of high affinity, regardless of its Km. | 130 | 4 | efbb74a4-a19f-48cc-bfb9-4cc40a30a222 | 2022 |
Acetyl-Coenzyme A (Acetyl-CoA) is a carrier of: | Amino groups in some transamination reactions. | Acetonitrile groups in some enzymatic reactions. | Ethyl groups in some enzymatic reactions. | Chemistry | Acetyl groups in some enzymatic reactions. | 131 | 3 | 00dee471-9442-41a7-bacf-6edfe8c3d802 | 2022 |
The oxidative degradation of acetyl CoA in the citric acid cycle gives a net result of all the following compounds, except: | 2 ATP. | 1 GTP. | 2 CO2. | Chemistry | 3 NADH. | 132 | 2 | bf2534d1-05d9-4ef1-8b3b-f3e7decb5b89 | 2022 |
In contrast to the resting state, actively contracting human muscle tissue exhibits: | A higher concentration of ATP. | A higher rate of lactate formation. | A lower consumption of oxygen. | Chemistry | A lower consumption of glucose. | 133 | 1 | 0ba25978-3772-46cb-98d3-ca59b9d1b0b4 | 2022 |
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