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Regarding the analytical technique of nephelometry, indicate the correct answer: | It is an analytical procedure based on the loss of radiation transmitted when passing through a suspension. | The detector is positioned at a 180º angle with respect to the light beam that is incident on the sample. | It can be carried out without a problem with a spectrophotometer. | Chemistry | It is an analytical procedure based on the dispersion of radiation when passing through a suspension. | 23 | 3 | 73dc5eca-7240-47a8-ab83-4c8ca8bb217a | 2023 |
Sensitivity is an analytical property that is defined as: | It is the relationship that exists between the variation of the analytical signal or change in the instrumental response with a change in the concentration of the analyte. | Minimum analyte concentration that generates a signal statistically distinguishable from the blank signal. | Ability of an analytical method to uniquely determine the analyte of interest. | Chemistry | Minimum concentration of analyte that can be accurately quantified. | 24 | 2 | d95b26b6-8820-43b9-885b-e6bf47846df5 | 2023 |
Regarding the Hook effect, or hook effect, indicate the correct answer: | It is a phenomenon that occurs with very high concentrations of antigen in immunoassays. | It is a phenomenon observed in immunoassays that provides falsely elevated analyte concentrations. | It is a positive interference observed in one-step "sandwich" immunoassays. | Chemistry | It is a phenomenon of cross-reactivity driven by analytes with a structure similar to that of interest. | 25 | 2 | bee42ecf-7221-43ec-86f3-ca786c6437e0 | 2023 |
Of the following elements, which one cannot be measured by inductively coupled plasma mass spectrometry (ICPMS)?: | Beryllium. | Chlorine. | Iodine. | Chemistry | Lithium. | 26 | 1 | cf2533ae-29de-4730-971c-1c08f91d9a10 | 2023 |
Regarding the theories of chromatography, indicate the incorrect answer: | The efficiency of the column is greater the smaller the height of the theoretical plate (H). | The height of the theoretical plate (H) is inversely proportional to the flow rate of the mobile phase. | The swirling diffusion or Eddy diffusion is part of the kinetic theory of chromatography. | Chemistry | The number of theoretical plates (N) is inversely proportional to the retention time of the solute. | 27 | 3 | f38b7a3c-cc78-4b28-9ce3-40bf19b70681 | 2023 |
The ethylenediaminetetraacetic acid (EDTA) is a chelating agent widely used in chemical analysis, and it is considered a ligand. | Bidentate. | Monodentate. | Hexadentate. | Chemistry | Tetradentate. | 28 | 4 | 19ef0243-20f1-486d-bd82-fa6bdb4dee13 | 2023 |
We have two dilute aqueous solutions of ammonium fluoride, one of 0.40 M and the other of 0.10 M. Given data: pKa(HF): 3.20 pKa(NH4+): 4.75 It is complied that: | The 0.10 M solution is more acidic than the 0.40 M solution. | The 0.40 M solution is more acidic than the 0.10 M solution. | Both solutions have the same pH. | Chemistry | Both have a basic pH, but it cannot be said which is more acidic with the data provided. | 29 | 4 | 57b616fa-d757-4130-955f-562184ce8abc | 2023 |
According to the CLP Regulation (Classification, Labeling and Packaging of substances and mixtures regulation), what are the hazard statements called? | H Phrases. | P phrases. | S Phrases. | Chemistry | R Phrases. | 30 | 2 | 1b7c7c4b-9b74-427e-9881-ae2aec80a026 | 2023 |
When we detect a possible anomalous data point within a set of data, it is necessary to: | Apply a Student's t-test to evaluate whether it can be rejected or not. | Apply a Dixon's Q test to evaluate whether it can be rejected or not. | Apply a Fisher's F test to evaluate whether it can be rejected or not. | Chemistry | Remove it from the data series before processing them. | 31 | 1 | 5f47fa8b-88ab-4537-b61d-3910c49d17d9 | 2023 |
Out of the following statements regarding atomizers in atomic spectroscopy, indicate which one is correct: | The use of hydride generation, as a preliminary stage to atomization in flame or plasma, is a discontinuous sample introduction system. | Solid samples can be introduced into plasmas for atomization by vaporizing them with a spark or a laser beam. | Electrothermal atomizers are continuous atomization devices that allow the atomization of solid, liquid, and gaseous samples. | Chemistry | Both plasma and flame are discontinuous atomization systems that require prior nebulization of the sample. | 32 | 1 | 677d8075-4c26-4194-9187-d6c739527e77 | 2023 |
A solution of acetic acid with a concentration of 0.1 M has a calculated pH of 2.9. What happens if we add sodium acetate? | The pH of the solution does not change, the addition of salts does not alter the pH value. | The pH of the solution will be less than 2.9. | Increase the temperature of the solution and the pH is not altered. | Chemistry | The pH of the solution will be higher than 2.9. | 33 | 3 | f1bc1655-cd07-4394-865e-6e8dd8639d11 | 2023 |
What type of radiation source can be used in molecular absorption spectrometry to perform measurements at a wavelength of 220 nm? | Hollow cathode lamp. | Deuterium lamp. | Globar Source. | Chemistry | Tungsten lamp. | 34 | 1 | fc72428b-4da0-4a03-a946-36c1ab7ab5e7 | 2023 |
Which detector is used in infrared absorption spectrometry? | Pyroelectric. | Photomultiplier. | Proportional counters. | Chemistry | Interferometer. | 35 | 2 | 7ed4808a-7ad9-4026-88c9-c577081e6330 | 2023 |
What is the basis of ion exchange chromatography? | Ionic exchange equilibria between the ions in solution and the ions on the surface of a solid (stationary phase). | An equilibrium distribution of the analyte between an aqueous phase and a stationary phase coated with a nonpolar solvent. | The separation of compounds based on their size. | Chemistry | Solid-liquid adsorption equilibria. | 36 | 2 | a8e1b1b7-7d8b-4735-83b7-ed947b8e6473 | 2023 |
What is chemiluminescence?: | Process of light radiation emission produced by a molecule, which has been previously excited by electromagnetic radiation. | A non-radiative deactivation process in which the molecule transitions from an excited vibrational level to a lower vibrational level situated within the same electronic state. | Process of emission of luminous radiation produced by a molecule previously excited by the energy released in a chemical reaction. | Chemistry | Non-radiative deactivation process due to the interaction between the luminescent species and another species present in the environment. | 37 | 4 | 757c54dc-2d67-4871-b8da-7c03b554ffc2 | 2023 |
Glass membrane electrodes are used for direct pH measurement. In this type of electrodes, which is the electrode that acts as a reference electrode? | Ag(s)|AgCl(s)|H+(1.0 M). | Ag(s)|AgCl(s)|Cl-(1.0 M). | Hg(l)|Hg2Cl2(s)|H+(1.0 M). | Chemistry | Pt|H2(g, 1 bar)|H+(1.0 M). | 38 | 1 | b155e727-e99c-4f0b-8dc5-3951cf20aacf | 2023 |
The existence of electroosmotic flow must be taken into account in: | Ion chromatography. | Pulse Voltammetry. | Capillary Electrophoresis. | Chemistry | Supercritical Fluid Chromatography. | 39 | 4 | 03356df0-0507-44aa-bf6f-51d8b1151b21 | 2023 |
What is produced when the nucleus of a certain isotope of Titanium undergoes electron capture? | Another isotope of Ti, different from the initial one. | A Ti- anion. | An isotope of Sc. | Chemistry | An isotope of V. | 40 | 4 | ff099522-18ca-4643-9f7d-d4916066d267 | 2023 |
How many microstates does a C atom present? | 6. | 2. | 20. | Chemistry | 15. | 41 | 3 | 637663c4-33c7-42b0-82aa-3711346b2a55 | 2023 |
Which molecule can be used to determine the covalent radius of O? | Dioxygen (O2). | Hydrogen peroxide (H2O2). | Carbon dioxide (CO2). | Chemistry | Ozone (O3). | 42 | 1 | ff5ffb68-d5dc-42a4-b832-ec8413e5b161 | 2023 |
What is the geometry of BrF3? | Flat triangular, with a fluorine in the center of the triangle. | Flat triangular, with the bromine in the center of the triangle. | In T shape. | Chemistry | Trigonal pyramidal (analogous to NH3). | 43 | 4 | acbf21f0-b656-4dd9-921d-62b1fd9824e0 | 2023 |
Which of these atoms give rise to H bonds? | N and Cl. | N and P. | O and Br. | Chemistry | O and C. | 44 | 2 | fffb987b-dc72-4e1b-8dfd-3cbca762bfa7 | 2023 |
What chemical compound is cristobalite a polymorphic form of? | SiO2. | TiO2. | ZrO2. | Chemistry | MnO2. | 45 | 2 | ad09caec-a729-4ef8-acfa-a7475b5e11d5 | 2023 |
What is the main component of porcelain? | The feldspar. | The alumina. | The clay. | Chemistry | The quartz. | 46 | 4 | 40602ad4-6939-48f1-b6b0-6dcedc56f6ec | 2023 |
What is sintering?: | It is the preparation of small particles from larger particles at high temperature. | It is the preparation of small particles from larger particles at low temperature. | It is the coalescence of particles from a powder aggregate through diffusion that takes place at high temperature. | Chemistry | It is the coalescence of particles from a powdered aggregate by diffusion that takes place at low temperature. | 48 | 4 | 30b624f6-301d-4e10-b823-3fa2945447ea | 2023 |
What metals make up the alloy known as brass? | Copper and nickel. | Iron and nickel. | Copper and zinc. | Chemistry | Iron and zinc. | 49 | 4 | 29a1b001-b2c7-45bb-9bba-460d8503dbe4 | 2023 |
Does metallic magnesium generate a hydrogen current when in contact with water? | No, because magnesium is covered with a layer of Mg(OH)2 when it begins to react with water. | No, it is not sufficiently reducing. | No, because the reaction of magnesium with water yields MgO and MgH2. | Chemistry | No, because Mg oxidizes the water to oxygen. | 50 | 2 | 2fbafc60-3c5e-46d6-a84b-0337826cad46 | 2023 |
Does iodine at room temperature appear as a dark solid with a metallic shine? | No, iodine at room temperature is a reddish liquid. | No, iodine at room temperature is a green gas. | Yes, because the solid is composed of a body-centered cubic lattice. | Chemistry | Yes, because, even though the solid is made up of I2 molecules, the intermolecular distance between two neighboring iodine atoms is smaller than the sum of the Van der Waals radii. | 51 | 3 | 5351e4ea-5c5b-46f5-9f28-47dc1efa5a46 | 2023 |
What is the oxidation state of the carbon atom in formaldehyde (methanal)?: | 2. | 4. | -2. | Chemistry | 0. | 52 | 3 | a3955b4b-4cac-428a-8d29-01fbf291de89 | 2023 |
What are the stoichiometries of the fluorine compounds with titanium? | TiF, TiF3 and TiF5. | TiF3 and TiF4. | TiF2, TiF4 and TiF6. | Chemistry | TiF3, TiF4 and TiF5. | 53 | 1 | b10bf959-8147-4f49-9f14-da95e6d6d244 | 2023 |
What are the solutions of KMnO4 in water like?: | Yellow and oxidizing. | Violets and oxidants. | Yellow and reducing. | Chemistry | Violets and reducers. | 54 | 1 | cb002479-745e-45e3-b654-be1aa1dcb2c2 | 2023 |
Given the following reaction (unbalanced), indicate which of the following statements is correct: x N2H4 (l) + y H2O2 (l) → z N2 (g) + t H2O (g): | This is an acid-base reaction in which hydrazine acts as an acid and hydrogen peroxide as a base. | x = z = 1 ; y = 2 ; t = 4. | This is a redox reaction in which hydrogen peroxide acts as a reducer and hydrazine acts as an oxidant. | Chemistry | This is a disproportionation reaction between hydrazine and hydrogen peroxide. | 55 | 1 | 555880a3-a0a2-444f-941f-e8c2d20dead3 | 2023 |
What is the maximum valence that the element with atomic number 42 can display? | +3. | +2. | +6. | Chemistry | +5. | 56 | 4 | 70785f94-94b5-42a5-80db-8772fd4727a9 | 2023 |
It is known as efflorescence: | The spontaneous redox reaction that occurs between an oxidant and a reducing agent, which are part of the same compound, when it is exposed to heat. | The property that some minerals and chemicals have to turn into powder by themselves, due to the loss of crystallization water, when exposed to air. | The process of protonation of metallic sulfides with strong acids that generates the release of hydrogen sulfide gas. | Chemistry | To the flotation phenomenon experienced by slag in the metallurgical processes of blast furnaces. | 57 | 1 | 825b7379-16a5-4f9c-b863-8a59939612d9 | 2023 |
In which of the following sets are all species paramagnetic?: | NO, O2, OF. | NO, CO, CN-. | NO-, O22-, N2. | Chemistry | NO+, O2+, OF+. | 58 | 2 | 61b6e32e-0eed-4046-bb63-76730a8ceceb | 2023 |
Regarding the stabilization energy of the crystal field (EECC), it can be asserted that: | The differences between the octahedral and tetrahedral crystal field splitting are maximal for the high-spin d3 and d8 cases, and these are the electronic configurations for which we find fewer tetrahedral complexes. | Since Δoct is 4/9 of Δtet, the crystal field stabilization energy (CFSE) of an octahedral environment is always less than that of an isoelectronic tetrahedral environment. | The tetrahalogenonickelate(II) ions, [NiX4]2-, where X is chloride, bromide or iodide, do not exist as such in tetrahedral form but instead acquire other ligands (such as water molecules) to achieve an octahedral environment. | Chemistry | The vast majority of nickel(II) complexes are octahedral. Especially those with large ligands, negative charge, and weak field (that is, ligands low in the spectrochemical series). | 59 | 2 | 613de06e-8220-45d0-a7f2-602258baed4c | 2023 |
The composition of the well-known "milk of magnesia" that is used to treat indigestion is: | Magnesium Phosphate. | Magnesium sulfate. | Magnesium hydroxide. | Chemistry | Magnesium Hydroxysulfate. | 60 | 4 | 51b773f8-0875-40b1-9f84-97f43e705e25 | 2023 |
What is the reaction called in which the same species is oxidized and reduced simultaneously? | Stoichiometry. | Dissociation. | Switching. | Chemistry | Disproportionation. | 61 | 3 | 15a76bc2-848d-4d8b-bc53-a5dbb650bff7 | 2023 |
What is the coordination number of a sphere in a close packing arrangement? | 8. | 14. | 10. | Chemistry | 12. | 62 | 3 | 754e0b18-4439-41b6-beba-e385bdd355f3 | 2023 |
To which of these symmetry groups can a chiral molecule belong?: | C1. | Ci. | Td. | Chemistry | Cs. | 63 | 2 | 2a95d1f2-097d-4975-85c9-e265e2e12cb8 | 2023 |
The carbon steel is: | A substitution alloy. | An intermetallic compound. | A pure product. | Chemistry | An interstitial alloy. | 64 | 3 | 53fea340-5411-474a-a6ba-c32b3ea92d06 | 2023 |
What is the structure of FeCr2O4? | Inverse spinel. | Normal Spinel. | Corundum. | Chemistry | Perovskite. | 65 | 1 | 0de207d0-c768-488b-b34a-30ebfb96c0fd | 2023 |
Which of the following coordination complexes satisfies the 18 electron rule?: | [Ni(en)3]2+ (en = ethylenediamine). | [Rh(CO)2Cl2]–. | [CpMn(CO)3] (Cp = cyclopentadienyl). | Chemistry | [Fe(CN)6]3–. | 66 | 4 | 8a4681c0-6ef0-47df-8839-87d57f8a6eb9 | 2023 |
Which of the following reactions is not suitable for the preparation of HBr?: | 3 KBr + H3PO4 (conc.) → K3PO4 + 3 HBr. | 2 KBr + H2SO4 (conc.) → K2SO4 + 2 HBr. | H2 + Br2 (g) → 2 HBr. | Chemistry | PBr3 + 3 H2O → H3PO3 + 3 HBr. | 67 | 1 | bfef0db0-3bfe-4a53-8f0b-ab58863762a2 | 2023 |
Considering their molecular orbital diagrams, which of the following statements is false?: | Molecular oxygen in its ground state is a paramagnetic gas. | The C2 molecule has a C-C bond order of 2. | The value of the spin multiplicity of molecular oxygen in its ground state is 3 (triplet state). | Chemistry | The Be2 molecule has a Be-Be bond order of 1. | 68 | 3 | fb2774a0-26f1-4c7a-82dc-09469c509331 | 2023 |
Which of the following species is not among the components of photochemical smog?: | NO2. | O3. | CH4. | Chemistry | SO2. | 69 | 3 | 87079a33-2467-4343-9f89-07029b3c1cc3 | 2023 |
Which of the following statements regarding the atmospheric chemistry of hydroxyl radicals is correct?: | Hydroxyl radicals do not react with sulfur dioxide. | Hydroxyl radicals do not react with carbon monoxide. | Hydroxyl radicals can undergo chain termination reactions when they interact with hydroperoxyl radicals. | Chemistry | The hydroxyl radicals do not react with hydrogen sulfide. | 71 | 4 | 42b282ee-7c10-4cbf-b1b5-398dd82625eb | 2023 |
What species results from the reaction of elemental sulfur with sulfite ion?: | Dithionite ion. | Dithionite ion. | Disulphite ion. | Chemistry | Thiosulfate ion. | 72 | 3 | d0f2e284-a8ac-4367-ad2b-a50701a10eb7 | 2023 |
Asbestos were widely used for their mechanical strength and heat resistance at a relatively low cost, and later abandoned as they are dangerous to health. How are the silicate tetrahedrons grouped in them? | Double silicates containing Si2O76- ions. | Simple silicates containing isolated SiO44- ions. | Silicates forming chains and/or sheets. | Chemistry | Cyclosilicates. | 73 | 4 | f19d8e42-63de-40ad-8ca2-06cadabfdc99 | 2023 |
What is emitted when a radio-226 nucleus transforms into a radon-222 nucleus? | Beta type radiation. | Alpha type radiation. | X-Radiation. | Chemistry | Gamma radiation type. | 74 | 1 | 4c5b9064-bc68-45f1-82a3-5e5451d8198a | 2023 |
What fairly common species in drinking water can, in excessive concentration, cause methemoglobinemia or "blue baby syndrome"? | Copper(II). | Iron(III). | Sulfate. | Chemistry | Nitrate. | 75 | 3 | 8f570d6a-d09c-4e0a-b34b-b242f18fe4f1 | 2023 |
How many unpaired electrons does copper(I) have in 3d orbitals? | One. | None. | Three. | Chemistry | Two. | 76 | 1 | c6da4443-472a-4fe3-9fc5-8582fcc7d6bc | 2023 |
What is the formula for phosgene? | COCl2. | POCl3. | SOCl2. | Chemistry | NO2Cl. | 77 | 2 | d0de4867-4434-42cf-8f26-2294e47e9d38 | 2023 |
What is obtained when reacting, under appropriate conditions, 10 grams of hydrogen and 32 grams of oxygen? | 32 grams of water. | 16 grams of water. | 72 grams of water. | Chemistry | 36 grams of water. | 78 | 3 | 8a32e156-7d4b-4e39-942a-0464c356b82e | 2023 |
Can hydrofluoric acid be stored in a glass bottle? | Yes, if the glass is amber-colored. | Yes, glass is very inert. | No, it reacts with glass producing fluorine. | Chemistry | No, it reacts with glass to produce SiF4. | 79 | 3 | e24e9cd1-9d68-4d5d-ae40-456d975d370a | 2023 |
Which of the following acids is strongest?: | HI. | HCl. | HNO3. | Chemistry | H2SO4. | 80 | 2 | f5168e77-6601-488d-ae4c-ed74759254cd | 2023 |
A chemical reaction that occurs at constant temperature and pressure is spontaneous when: | The variation of reaction enthalpy is negative. | The Gibbs energy change of reaction is zero. | The variation of reaction enthalpy is equal to zero. | Chemistry | The Gibbs energy variation of the reaction is negative. | 81 | 3 | 3bbda9fa-93b6-4245-b4cb-85a17d7cf646 | 2023 |
Relaxation methods in Chemical Kinetics are used for: | Determine the reaction rate by modifying the equilibrium in a reactive system. | Determine the concentrations of the reacting species by modifying the equilibrium in a reactive system. | Determine the rate constants by modifying the equilibrium in a reactive system. | Chemistry | Determine the equilibrium constant by modifying the equilibrium in a reactive system. | 82 | 4 | 02af0131-612c-433f-bf60-b21326beeb56 | 2023 |
How does temperature affect the Maxwell distribution of molecular speeds? | As the temperature increases, the most probable speed increases and the number of molecules that have that speed decreases. | At low temperature, the maximum of the distribution function is located at high speeds. | At a low and fixed temperature, the distribution functions of molecular speeds of two gas samples of different molecular mass are such that the lighter gas has the highest speeds at lower velocities. | Chemistry | At high temperature, the distribution function presents a very high and narrow peak in the region of high speeds. | 83 | 2 | fd79d1f6-9e0a-469c-af2a-595529a27102 | 2023 |
Which statement is correct regarding the properties of water?: | The melting temperature is not affected by the increase in pressure, but there is an increase in volume during melting. | The melting temperature decreases as the pressure increases as a result of the increase in volume during melting. | The melting temperature decreases as the pressure increases due to the reduction in volume during melting. | Chemistry | The increase in pressure does not change the melting temperature or the volume. | 84 | 4 | 46f04c67-e986-40d8-bf07-7bd9117b645d | 2023 |
What is a state equation? | It is a mathematical equation that describes the probability of a state. | It is an equation that allows calculating the enthalpy change in a thermodynamic process. | A mathematical function that relates different state variables without having to resort to experimentation. | Chemistry | It is a mathematical function that allows calculating the kinetic constant of a chemical reaction. | 85 | 4 | 0512e761-1a49-4fb7-b34f-792dcc8aeeee | 2023 |
Indicate the units of the rate constant of a reaction that follows the kinetic law v = k [A][B][C]: | M-1 s-1. | M-2 s-1. | s-1. | Chemistry | M s-1. | 86 | 1 | cfcbc98b-b8fc-4d82-a99d-a098de7837a7 | 2023 |
Indicate the correct statement about thermodynamic state functions: | The Gibbs energy is the sum of the internal energy plus the product of entropy and temperature. | Enthalpy is the sum of the internal energy plus the product of pressure and volume. | The Helmholtz energy is the sum of the enthalpy plus the product of pressure and volume. | Chemistry | The internal energy is defined as the Helmholtz energy minus the product of temperature and entropy. | 87 | 1 | 28551b76-92be-43df-95f3-a4e9e6fce3b6 | 2023 |
What quantities are necessary to obtain the molar enthalpy of a reaction at a temperature different from the standard? | The molar heat capacities at constant pressure of the reactants and products are needed under the desired conditions. | It is enough to know the standard reaction enthalpy and the temperature at which you want to calculate the molar reaction enthalpy. | The molar enthalpy of reaction is independent of the temperature. | Chemistry | If the reaction involves gaseous substances, the variation of the reaction volume is needed. | 88 | 2 | 6e35c852-3c1e-4b23-a6c7-f8e666ccaac6 | 2023 |
The Boltzmann distribution function: | It describes the spatial distribution of molecules associated with chemical systems in equilibrium. | Describes the energy distribution associated with chemical systems in equilibrium. | It is independent of the temperature. | Chemistry | Describes the energy distribution associated with chemical systems in equilibrium or out of equilibrium. | 89 | 1 | ede0cd05-5aea-4acf-b011-7b7609bfbabd | 2023 |
How does the molar conductivity of an electrolyte vary with an increase in its concentration? | When the concentration of an electrolyte increases, the number of ions present in the solution also increases, therefore the molar conductivity also increases. | By definition, molar conductivity is an intensive magnitude that does not depend on concentration. | For weak electrolytes, molar conductivity increases with concentration, while for strong electrolytes the relationship is inverse. | Chemistry | The molar conductivity always decreases when the concentration of the electrolyte increases. | 90 | 3 | d0607a81-a494-4e01-8abc-a6d2c63ea814 | 2023 |
Which statement is correct regarding the potential energy surface associated with a chemical reaction?: | The comparison of the energy of the products with that of the reactants provides information about the kinetics of the reaction. | The reactants, products, and reaction intermediates correspond to minima of the potential energy surface. | The concept of potential energy surface arises directly from the Schrödinger equation. | Chemistry | It is impossible to obtain information about the kinetics of the reaction from its potential energy surface. | 91 | 1 | 28e8c6da-375d-4b41-90d5-22f69f3bb4f2 | 2023 |
Which statement is correct in relation to the Hartree-Fock equations of computational chemistry?: | To obtain the Hartree-Fock equations from the Schrödinger equation, it is necessary to assume that the atomic nuclei remain approximately fixed during the movement of electrons. | These equations aim to computationally obtain the energy of a reaction. | To obtain the Hartree-Fock equations, it is assumed that the wave function is a product of functions associated with the electrons present in the chemical system. | Chemistry | These equations are based on the theory of repulsion of electron pairs in the valence shell. | 92 | 2 | 5a0926fb-0238-4f69-a94d-44d01e4a24f3 | 2023 |
If an exothermic reaction is carried out under adiabatic conditions and at constant pressure: | The enthalpy of the products will be less than that of the reactants. | The enthalpy of the products will be greater than that of the reactants. | The temperature of the products will be lower than that of the reactants. | Chemistry | The temperature of the products will be higher than that of the reactants. | 93 | 3 | 4a553da0-81fb-429e-b40b-60c5b6606acf | 2023 |
The criterion for material equilibrium, in a closed system capable of performing only pressure-volume work maintained at constant temperature and volume, is that: | The enthalpy of the system is minimal. | The internal energy of the system is minimal. | The Gibbs free energy of the system is minimal. | Chemistry | The Helmholtz free energy of the system should be minimal. | 94 | 3 | fd70589d-0a10-4ac9-a98f-c57bd3880370 | 2023 |
The chemical potential of solid glucose at 25ºC and 1 atm is: | Greater than the chemical potential of glucose dissolved in an unsaturated aqueous solution at 25ºC and 1 atm. | Lower than the chemical potential of glucose dissolved in an unsaturated aqueous solution at 25ºC and 1 atm. | Greater than the chemical potential of glucose dissolved in a supersaturated aqueous solution at 25ºC and 1 atm. | Chemistry | Just like the chemical potential of glucose dissolved in an unsaturated aqueous solution at 25ºC and 1 atm. | 95 | 2 | c18c7101-fa25-428e-994e-b6e0daf6a253 | 2023 |
At 25ºC, the addition of potassium nitrate, a salt soluble in water, to an aqueous solution of silver chloride, a salt slightly soluble in water, will cause: | An increase in the average ionic activity coefficient of silver chloride. | A decrease in the ionic strength of the solution. | An increase in the solubility of silver chloride. | Chemistry | A decrease in the solubility product constant of silver chloride. | 96 | 4 | 2b0ce026-576c-4fc9-8cad-baf34ae9dc19 | 2023 |
The normal mode of symmetric stretch vibration of the linear CO2 molecule is: | Active in the infrared and inactive in Raman. | Active in infrared and active in Raman. | Inactive in infrared and inactive in Raman. | Chemistry | Inactive in infrared and active in Raman. | 97 | 3 | 80fee030-069a-4800-9f3c-d4248e0fbfd6 | 2023 |
How many terms of electron-electron interaction potential energy does the Hamiltonian of the nitrogen atom have? | 21. | 6. | 10. | Chemistry | 15. | 98 | 2 | 6a11a21a-2dc6-43d7-b0a0-b0f2b85c005b | 2023 |
The enthalpy of sublimation of iodine at 25°C and 101.3 kPa is equal to: | The energy of the iodine-iodine bond. | The enthalpy of vaporization minus the enthalpy of fusion of iodine. | The enthalpy of formation of iodine in gas phase. | Chemistry | The enthalpy of vaporization of iodine. | 99 | 4 | e63eeb1a-06ca-45fc-9640-76df7334e87c | 2023 |
Given the standard reduction potentials Cu2+/Cu and Ag+/Ag, respectively +0.34 and +0.80 V, what is the standard Gibbs free energy of the reaction Cu + 2 Ag+ → Cu2+ + 2 Ag? | - 88780 J. | - 110010 J. | 0.46 J. | Chemistry | - 55005 J. | 100 | 2 | f57a5a5b-10e2-44fa-b6b0-6e1a0f9d4ef8 | 2023 |
In a reaction, if the reaction quotient, Q, is greater than Kc, the reaction will evolve: | Towards the decomposition of products into reactants. | Towards the formation of products. | It is impossible for Q to be greater than Kc. | Chemistry | It will not evolve, the system is in equilibrium. | 101 | 2 | edf9859d-fef1-4dce-8bd7-2bc9c0f4bb60 | 2023 |
In the electrolysis of an aqueous solution of common salt, 22.4 L of chlorine gas is obtained, measured at 1 atm and 0ºC. If the current intensity applied has been 2 A, the electrolysis time is: | (96500/2) s. | 96500 s. | 96500 min. | Chemistry | (96500 x 2) s. | 103 | 1 | ae8d16a9-2403-4d35-b55d-4f3fe7f98803 | 2023 |
The transport of matter in a solution can be due to diffusion (concentration gradient), migration (electric potential gradient), and convection (movement of the solution as a whole). Indicate which statement is true: | In a homogenized solution at rest and constant temperature of sugar in water, matter is transported by diffusion. | In a homogenized solution of sugar in water at rest and at a constant temperature, matter is transported by migration. | In a homogenized solution at rest and at constant temperature of sugar in water, there is no transport. | Chemistry | In a homogenized solution of sugar in water at rest and at constant temperature, matter is transported by diffusion, migration and convection. | 104 | 4 | 82a40fd4-e54b-4862-88a9-0121208dcade | 2023 |
For certain radical recombination reactions, such as for example, 2 CH3 → C2H6, it has been observed that the activation energy is practically zero. Consequently, these reactions: | They will be faster at lower temperatures. | They will be slower at lower temperatures. | They can never be spontaneous. | Chemistry | The rate constant of these reactions will essentially be independent of the temperature. | 105 | 3 | 4d5354a2-8e17-4ed7-99a9-8170e9abbaf1 | 2023 |
The Gibbs-Duhem equation is useful for: | Understand the dependence on temperature of the activity coefficient of the solute. | Obtain the activity coefficient of the solute if the one of the solvent is known. | Understand the dependence on pressure of the activity coefficient of the solvent. | Chemistry | Obtain the mean ionic activity coefficient of an electrolyte. | 106 | 1 | 67d02c7a-d5c6-412e-b7b8-666e27ce5d5b | 2023 |
It has been observed for a certain chemical reaction between ideal gases that the equilibrium constant increases as the temperature increases. From this it is deduced that: | ΔrG0 < 0. | ΔrS0 > 0. | ΔrH0 > 0. | Chemistry | ΔrG0 > 0. | 107 | 4 | 90f1f575-81cc-4534-9938-94c0aa3d7b6d | 2023 |
In a one-dimensional harmonic oscillator, the energy levels: | They increase their separation as energy increases. | They are so close to each other that it can be assumed that the energy varies continuously. | They are equidistant. | Chemistry | They are independent of the frequency of the oscillator. | 108 | 4 | 86aefb67-57bf-4600-af6d-1df864d7fd16 | 2023 |
The Born-Oppenheimer approximation: | Allows calculating the lattice energy of an ionic crystal. | Indicates that the square of the wave function gives the probability density of finding the particles in a given location in space. | Calculate π type molecular orbitals using only p type atomic orbitals. | Chemistry | Allows treating the electronic and nuclear movements independently. | 109 | 3 | 7807014f-41d0-44df-8172-590e64970619 | 2023 |
The gas-phase reaction between iodine monochloride (ICl) and hydrogen (H2) produces iodine and hydrogen chloride as products. The reaction mechanism is in two stages: Slow stage: H2 (g) + ICl (g) → HI (g) + HCl (g) Fast stage: HI (g) + ICl (g) → I2 (g) + HCl (g) What is the rate equation?: | Speed = k[H2][ICl]2. | Speed = k[H2][ICl]. | Speed = k[HI][ICl]. | Chemistry | Speed = k[H2][ICl]/([HI][HCl]). | 110 | 1 | b5e6af48-b570-4fa3-9b4d-fef2d0c154aa | 2023 |
The reaction 2 SO2 (g) + O2 (g) ⇌ 2 SO3 (g) has a ΔrHo value of -198 kJ·mol-1. What effect does an increase in temperature have? | The formation of SO2 is favored. | It does not affect the equilibrium, only the reaction rates. | The formation of SO2 and SO3 is favored. The reaction rate does not change. | Chemistry | The formation of SO3 is favored. | 111 | 2 | 7fff03bd-d055-4958-b3d8-f52915bfe063 | 2023 |
Regarding the photoelectric effect, what parameter should we increase to achieve an increase in the kinetic energy of the emitted electrons? | The wavelength of the radiation. | The intensity of the radiation. | Both the intensity and the frequency of the radiation. | Chemistry | The frequency of radiation. | 112 | 3 | dccc5752-85d9-4c93-95ad-f193f2d994ec | 2023 |
For the fusion of ice at 0ºC and 1 atm, it holds true that: | The variation of Helmholtz free energy is zero. | The variation of Gibbs free energy is zero. | The enthalpy change is zero. | Chemistry | The entropy variation is zero. | 113 | 1 | dcd60f60-ab12-43ca-83ad-3e25bb955368 | 2023 |
Which compound has the lowest boiling point at 1.0 atm pressure? | C2H6. | CH4. | CCl4. | Chemistry | Cl2. | 114 | 1 | 29912888-72f5-4d00-8386-e299a8fca4a7 | 2023 |
Which of the following statements about the relative energy levels of the molecular orbitals for the O2 molecule is incorrect?: | σ2s < σ2p. | σ2s < σ*2s. | σ*1s < σ2s. | Chemistry | π2p < σ2p. | 115 | 3 | 196bc39e-3096-4284-957b-b9e8717bb86b | 2023 |
Which of the following material-colloid combinations is incorrect?: | Smoke-aerosol. | Mayonnaise-emulsion. | Opal-solid solution. | Chemistry | Pumice stone - solid foam. | 116 | 4 | ab53f686-50ee-4da9-9c88-d57fa2073e33 | 2023 |
8.0 moles of CO react with 4.0 moles of O2 to produce 8.0 moles of CO2 at 25°C and 1.0 bar. If 566.0 kJ are released in the reaction and PΔV equals -2.5 kJ, then: | ΔH° = -566.0 kJ and ΔU = -568.5 kJ. | ΔH° = -566.0 kJ and ΔU = -563.5 kJ. | ΔH° = +566.0 kJ and ΔU = +563.5 kJ. | Chemistry | ΔH° = +566.0 kJ and ΔU = +568.5 kJ. | 118 | 1 | 94ce8e72-1009-4c41-93d8-71b9bb955afe | 2023 |
The atoms that least scatter X-ray radiation are those of: | Nitrogen. | Hydrogen. | Rhenium. | Chemistry | Chlorine. | 119 | 1 | 58b63781-c389-4b00-8dab-1d0f5b0665d7 | 2023 |
The attraction forces between neutral species (atoms or molecules, but not ions) are known as: | Dipolar. | Van der Waals forces. | Ionic. | Chemistry | Induced dipole. | 120 | 1 | d73bd6c2-01c6-4673-af4e-fe3e59c069f4 | 2023 |
The enthalpy change for the formation of one mole of a compound directly from its elements is known as: | Combustion heat. | Entropic heat. | Initiation heat. | Chemistry | Standard heat of formation. | 121 | 3 | c5b7299e-0213-4e05-810d-4d5f7bbd1c6f | 2023 |
The hybridization of carbon in ethylene is: | s. | sp. | sp2. | Chemistry | sp3. | 122 | 4 | 59c1f69b-37cf-4c1f-a653-d12651eb16d9 | 2023 |
The dehydrohalogenation of alkyl halides by alkoxide bases occurs through the mechanism: | E1. | E2. | SN2. | Chemistry | SN1. | 123 | 1 | 58886a45-ecc5-4de2-b0f6-d2ff47f85a8b | 2023 |
In Nuclear Magnetic Resonance, the dependence of the resonance position of a nucleus that results from its molecular environment is called: | Induced field. | Electronic coupling. | Spin-spin coupling. | Chemistry | Chemical shift. | 124 | 3 | 83696500-748c-46c5-baa5-44cfda4b6a8f | 2023 |
The sequence of forming a Grignard or alkyl lithium reagent (also called metalation) followed by hydrolysis converts a haloalkane into a: | Alcohol. | Alkane. | Carboxylic acid. | Chemistry | Aldehyde. | 125 | 1 | 3f70b107-ede1-4b48-99ee-f0025fd50c9e | 2023 |
The catalyst consisting of palladium precipitated on calcium carbonate with lead acetate and quinoline is known as: | Lindlar Catalyst. | Heck Catalyst. | Suzuki Catalyst. | Chemistry | Perkin's Catalyst. | 126 | 2 | 4ef7c6a4-5a98-475a-8eb4-88e76928d63e | 2023 |
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