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In enzymatic studies, a sigmoid curve when representing the substrate concentration [S] versus the reaction speed [V] indicates: | Cooperative union. | Michaelis-Menten kinetics. | Non-competitive inhibition. | Chemistry | Competitive inhibition. | 29 | 2 | d834fbc0-e9ad-4832-a4c3-aee35374628a | 2021 |
Which of the following statements is correct for biological membranes?: | Cholesterol forms stable associations with sphingolipids, constituting thicker and less fluid microdomains called lipid rafts. | They are supported by covalent bonds between their components: phospholipids, cholesterol and proteins. | The percentage by weight of protein does not vary among different cell types. | Chemistry | They are symmetrical, with a similar distribution of phospholipids in both hemimembranes. | 30 | 2 | 93c95fb3-a01c-4a79-ad70-11e13b23dd9d | 2021 |
Where is the enzyme glucokinase located? | Skeletal muscle. | Liver. | Adipose tissue. | Chemistry | Kidney. | 31 | 1 | 78bfbfe4-1b40-404c-ad51-1a77c58b28cf | 2021 |
The chylomicrons are: | Small particles poor in triglycerides and rich in cholesterol. | Small particles that primarily contain proteins, cholesterol, and phospholipids. | Large particles produced by the liver involved in the reverse transport of cholesterol. | Chemistry | Large particles produced by the intestine that transport dietary lipids to the tissues. | 32 | 3 | 2b8d81c1-733c-4ef1-ab09-bd36667c633b | 2021 |
Which of the following statements is correct for the metabolism of glycogen?: | The glycogen phosphorylase kinase releases glucose-1- phosphate from the non-reducing ends of glycogen. | The glycogen phosphorylase only presents two conformational states, being more active if it is not phosphorylated. | The glycogen phosphorylase releases glucose-6-phosphate, which can directly enter glycolysis. | Chemistry | The glycogen synthase is inhibited by phosphorylation. | 34 | 3 | 212deac0-1b78-480d-80f5-7d4cbf21d2c6 | 2021 |
Which of the following statements is correct for telomeres?: | They allow the shortening of chromosomes, which without these structures would lengthen with each replication. | They are unique structures located inside the chromosomes. | In certain cancerous processes, telomerase, the enzyme responsible for its replication, is abnormally reactivated. | Chemistry | They are replicated by telomerase, which has high activity in all cells. | 35 | 4 | b2f1e411-386d-424a-806e-98ad315eef10 | 2021 |
The indoles are: | Very weak bases. | Very weak acids. | Strong bases. | Chemistry | Strong acids. | 36 | 2 | 98f5c088-9092-495a-924f-93f2521bd6d3 | 2021 |
Which of the following statements is not true?: | Butane is a homologue of propane. | Hexane has five constitutional isomers. | When naming substituents in alphabetical order, the prefix iso- is considered part of the name of the alkyl group. | Chemistry | The general formula CnH2n+2 is valid for linear alkanes but not for branched ones. | 37 | 3 | a0c3bc02-7186-467e-8a18-55a1f56a2888 | 2021 |
What is the appropriate sequence of reactions to obtain 1-isopropyl-2-nitro-benzene from benzene? | (a) A Friedel-Crafts reaction; followed by (b) a sulfonation reaction; followed by (c) a nitration reaction, followed by (d) a desulfonation reaction. | (a) A nitration reaction, followed by (b) a Friedel-Crafts reaction. | (a) A nitration reaction, followed by (b) a sulfonation reaction, followed by (c) a Friedel-Crafts reaction, followed by (d) a desulfonation reaction. | Chemistry | (a) A Friedel-Crafts reaction, followed by (b) a nitration reaction. | 38 | 2 | 3a2fba3b-b3cd-4308-b764-0a0d6d22a818 | 2021 |
Which reagents allow obtaining cis-2-hexene from 2-hexyne? | H2/Lindlar catalyst. | H2/Pd(C). | NaH. | Chemistry | Na/NH3 (liq). | 39 | 2 | fd5816b1-fa4e-4005-93ff-4c6367c33bbd | 2021 |
The constitutional isomers that balance by the migration of an atom or group of atoms are: | Diastereoisomers. | Meso compounds. | Tautomers. | Chemistry | Enantiomers. | 40 | 4 | bf4b4006-bd3d-44db-98b0-12d96cb15478 | 2021 |
All of the following species are Lewis bases except for: 1: CH3OH 2: H2S 3: NH3 4: CH4 | 2. | 1. | 4. | Chemistry | 3. | 42 | 4 | bfe2e0ae-8623-4df2-a163-1c0e8cd21994 | 2021 |
Which of the following statements is false?: | SN1 reactions lead to total racemization. | The SN2 reactions are concerted. | The SN2 reactions proceed with inversion of configuration. | Chemistry | SN1 reactions can lead to rearrangement products. | 44 | 2 | fe7870b2-fad4-488b-9dfd-4673eff04fbb | 2021 |
When thiols are oxidized with iodine, the following are obtained: | Sulfones. | Sulfoxides. | Disulfides. | Chemistry | Sulfonic Acids. | 45 | 4 | 36e92bd5-fa52-408d-b228-fa03945c58fe | 2021 |
The reaction of aldehydes and ketones with primary amines leads to: | Secondary Amines. | Imines. | Ammonium salts. | Chemistry | Tertiary amines. | 46 | 1 | abe8bae6-59d3-479c-8839-cf49f24faafe | 2021 |
Which of the following phenolic compounds has the lowest pKa value?: | 3-methyl-5-nitrophenol. | 2,6-dimethyl-3-nitrophenol. | 2-methyl-6-nitrophenol. | Chemistry | Phenol. | 47 | 4 | 1ab72d8b-07e0-4b87-82b2-66da21038a7b | 2021 |
Which of the following statements is true?: | There are chiral compounds without stereocenters. | A molecule with asymmetric carbon atoms is chiral. | In a Fischer projection, the vertical bonds are projected as approaching the observer. | Chemistry | An optical purity of 72% in a sample means that there is 72% of the majority enantiomer. | 48 | 2 | 3da3076b-4d3e-47db-8f3f-4e25e0c11815 | 2021 |
Which of the following statements is not applicable to nitriles?: | Nitriles can be formed from alkyl halides when treated with alkaline salts of the cyanide ion. | Nitriles can be hydrolyzed to the corresponding carboxylic acids. | Nitriles can be formed by dehydration of amides. | Chemistry | Nitriles react with Grignard reagents to form tertiary alcohols. | 49 | 3 | 097bcdbc-1ea4-4fea-b2cf-2e2f97b3d911 | 2021 |
The elimination reaction on vicinal dihaloalkanes produces alkyl halides in the following manner: | Stereoselective. | Regioselective and stereospecific. | Diastereoselective. | Chemistry | Enantiospecific. | 50 | 1 | 8af00892-e534-4214-b1b0-65bf04e8f446 | 2021 |
Which of the following statements is not true?: | In the reaction of methyl iodide with sodium hydroxide to produce methanol, there are no intermediates. | A transition state cannot be isolated. | The unimolecular elimination E1 is a concerted reaction. | Chemistry | Dimethylformamide (DMF) is a polar aprotic solvent. | 51 | 4 | 797a3688-0f0f-4535-93b9-3636f5d63802 | 2021 |
In the treatment of (Z)-3-methyl-pent-2-ene with bromine water, after the elimination of the excess of this reagent, a reaction crude is obtained which in the polarimeter turns out to be: | Optically inactive, as it is a meso compound. | Optically active, as it is a chiral compound. | Optically inactive, as it is an achiral compound. | Chemistry | Optically inactive, as it is a racemic mixture. | 52 | 3 | 0c0e8cc1-9795-4465-b64a-ddba5e6d1675 | 2021 |
The cinnamic acid is a: | Fatty acid. | Terpene. | Phenylpropanoid. | Chemistry | Flavonoid. | 53 | 4 | dcf95abf-5f48-41be-9f04-42dc5b687486 | 2021 |
If a compound with the formula C10H18 consumes 2 moles of hydrogen in catalytic hydrogenation, how many rings does the compound consist of? | One. | Zero. | Three. | Chemistry | Two. | 54 | 1 | f69f5936-ce21-4c89-9686-f337db2cec95 | 2021 |
Sulfides react with alkyl halides to yield: | Thioethers. | Thiols. | Ammonium salts. | Chemistry | Sulfonium salts. | 55 | 3 | 1f384755-3aa5-4132-bb11-b4a4b5100034 | 2021 |
Which of the following reagents will not allow for the complete conversion of ethanol into the corresponding ethoxide anion?: | KOH. | Na. | K. | Chemistry | NaH. | 56 | 2 | 766a7b44-92df-4438-ba4a-bdb2a84bdd61 | 2021 |
Pyridines react with peracids to give: | Nitrones. | N-oxides. | Diazonium salts. | Chemistry | Amino acids. | 58 | 1 | 58177ed6-a63e-47dc-b8e0-dc3b8e2c091c | 2021 |
When sodium phenoxide is heated with carbon dioxide under pressure and then the reaction mixture is acidulated, salicylic acid is produced. This reaction is known as: | Kolbe-Schmitt. | Claisen. | Knoevenagel. | Chemistry | Diels-Alder. | 59 | 2 | 28e9bbcd-e442-4d7c-9861-9cbcaf205a16 | 2021 |
With bromine, the 2-pyrone forms an unstable intermediate that, when heated, produces: | 5-bromo-2-pyrone. | 6-bromo-2-pyrone. | 3-bromo-2-pyrone. | Chemistry | 4-bromo-2-pyrone. | 60 | 4 | 6339a53c-35f1-49ea-9421-199cb787269d | 2021 |
In the presence of soluble metal complexes such as Ni or Pd, alkyl halides undergo a reaction to form carbon-carbon bonds to form dienes. This process is called, reaction of: | Suzuki. | Sonogashira. | Negishi. | Chemistry | Heck. | 61 | 3 | deaa6d56-a50f-4c6a-b78d-c6e917065138 | 2021 |
When an aldose is treated with HCN, the following is obtained: | A cyanohydrin. | An aldehyde. | A diazonium salt. | Chemistry | An amine. | 62 | 2 | e7ffeb30-b937-4aad-a2b6-d6594dc4229b | 2021 |
In aromatic electrophilic substitution, the methyl and trifluoromethyl substituents behave as: | Deactivators. | Activators. | The methyl is activating and the trifluoromethyl is deactivating. | Chemistry | The methyl is deactivating and the trifluoromethyl is activating. | 63 | 4 | 540cc878-c395-4fed-bd06-2c14e8c31084 | 2021 |
What product is obtained when the compound CH3CH=CHCH2-C(=O)-CH3 is reduced with NaBH4? | CH3CH2CH2CH2-CH(OH)-CH3. | CH3CH=CHCH2-CH(OH)-CH3. | CH3CH2CH2CH2-C(=O)-CH3. | Chemistry | CH3CH2CH2CH2-CH2-CH3. | 64 | 1 | 1dd77292-cfb4-4b70-9e2a-c7607eb9bfd5 | 2021 |
The structural units responsible for the characteristic reactions of a molecule are known as: | Functional groups. | Stereogenic centers. | Asymmetric centers. | Chemistry | Chiral centers. | 65 | 2 | e2f2b336-7d09-4152-aa9a-370c8abc324f | 2021 |
In the reaction of cis- and trans-1-bromo-4-(1,1-dimethylethyl)cyclohexane with sodium methoxide: | A mixture of cis- and trans-4-(1,1-dimethylethyl)-1-methoxycyclohexane is produced. | Trans-4-(1,1-dimethylethyl)-1-methoxycyclohexane is produced. | 4-(1,1-dimethylethyl)cyclohex-1-ene is produced, with the reaction being faster if starting from the cis isomer of the starting substance. | Chemistry | The 4-(1,1-dimethylethyl)cyclohex-1-ene is produced, with the reaction being faster if it starts from the trans isomer of the starting substance. | 66 | 4 | 9ec94195-2254-43a7-9648-04255aa31ce4 | 2021 |
Which of the following statements is not true?: | Thiols have a higher pKa than alcohols. | A thiol is added to natural gas to detect leaks. | Thiols form complexes with heavy metals. | Chemistry | Thiols are easily oxidized to give disulfides. | 67 | 2 | a9880ec7-8720-470f-b571-080ed4219355 | 2021 |
Which of the following ions is antiaromatic?: | Cyclopentadienyl anion. | Cyclopentadienyl cation. | Cycloheptatrienyl cation. | Chemistry | Cyclopropenyl cation. | 68 | 1 | 927b352a-53ed-4dbf-848c-353a37c688ed | 2021 |
What organic product do you expect from the reaction between octanol and pyridinium chlorochromate in dichloromethane? | Octanal. | Octanoic acid. | Octane. | Chemistry | Chlorooctane. | 69 | 2 | 1a69792b-5a26-4d36-b4d5-ed704dae6e0d | 2021 |
If pentanal is treated with methylmagnesium bromide, what organic product do you expect to obtain after carrying out this reaction with an aqueous solution of HCl? | 2-Chlorohexane. | Pentanol. | 2-Hexanol. | Chemistry | Hexanal. | 70 | 4 | 46bc4ba0-2e23-4933-b7e8-ee8a3961c577 | 2021 |
Is sulfur hexafluoride, SF6, inert? | No, it reacts with water at room temperature. | Yes, it is very inert due to kinetic reasons. | Yes, it is inert because the sulfur is in the oxidation state +6. | Chemistry | No, it is a widely used fluorinating agent. | 71 | 1 | 7731cc3b-f21c-492a-9887-34a41d8c29bd | 2021 |
Which of the following statements about NaOH and Ca(OH)2 is true?: | Both react with atmospheric CO2. | The water solubility of Ca(OH)2 is much higher than that of NaOH. | Heated to similar temperatures, both transform into their oxides. | Chemistry | Both are industrially obtained through the same process: by electrolysis of their aqueous chloride solutions. | 72 | 2 | 25c781da-9c5f-42e1-b8c4-ee3917bd0dc6 | 2021 |
Knowing that it is polar, to which point group does the NHF2 molecule belong? | Sci. | CS. | Td. | Chemistry | D3h. | 73 | 1 | e73b3517-290a-42d0-8590-0a72e2c0da2f | 2021 |
What is the structure of beryllium oxide? | Structure of NaCl. | Diatomic molecules Be=O. | Chain structure -Be-O-. | Chemistry | Wurtzite structure. | 74 | 3 | b049dd5d-3f7b-4466-b663-7e1e90551e93 | 2021 |
Chrysotile or white asbestos is a silicate belonging to the group of: | Pyrosilicates. | Orthosilicates. | Phyllosilicates. | Chemistry | Tectoaluminosilicates. | 75 | 4 | f1b9e853-055c-411d-b5ec-56a025d6ffeb | 2021 |
The strength of the hydrogen bond decreases according to: | H-F > H-N > H-O. | H-F > H-O > H-N. | H-F < H-N < H-O. | Chemistry | H-F < H-O < H-N. | 76 | 1 | c55a7eff-a512-4404-88b0-99c7402792f3 | 2021 |
Is acid-base catalysis possible in organisms? | Yes, through metallic ions integrated into protein structures. | Yes, through free H+ or OH- ions. | No. Acid-base catalysis is absent in organisms, as they do not possess the extreme pH conditions that would allow it. | Chemistry | Yes, through free metallic ions. | 77 | 2 | 47d0bb69-6caa-45f4-9d36-194e86962c7b | 2021 |
What is the preferential corrosion along the grain boundaries in polycrystalline materials called? | Galvanic corrosion. | Stress corrosion. | Differential Aeration Corrosion. | Chemistry | Intergranular corrosion. | 78 | 3 | 660d0ae2-7ea3-4985-96c5-ba09fac14d18 | 2021 |
How is P4 industrially obtained? | From apatite by reduction with sodium. | From apatite through aqueous electrolysis. | From the apatite by reduction with carbon in an electric furnace. | Chemistry | From apatite by reduction with hydrogen. | 79 | 4 | 6820ceeb-53a5-463d-ad65-89311e28dc39 | 2021 |
For a metallic conductor, indicate which of the following statements is true: | Its electrical resistivity decreases as the temperature increases. | Its electrical resistivity increases as the temperature increases. | Its electrical resistivity is directly proportional to its conductivity. | Chemistry | Its electrical resistivity does not vary with temperature. | 80 | 1 | 6bcd802f-154c-4f8c-981c-1e23b857c2f7 | 2021 |
What is referred to as "water gas"? | To a mixture of H2 and CO. | Water in the state of vapor. | To a mixture of H2 and O2 just obtained by electrolysis of water. | Chemistry | To a mixture of H2 and O2 that react to produce water. | 81 | 2 | 58736d16-8b9b-44fd-ba18-7294c15393b5 | 2021 |
Which of the following species does not have at least one pair of geometric isomers? | [Co(H2O)3Cl3]. | [Co(H2O)4Cl2]+. | [Pt(NH3)2Cl2]+. | Chemistry | [Pd(NH3)Br3]-. | 82 | 3 | 344b0db5-3522-4d2e-b0b5-ae7b7a5f04f8 | 2021 |
What is creep? | It refers to the permanent deformation, independent of time, that occurs under stress, which is only significant at low temperatures. | It is the time-dependent permanent deformation that occurs under stress, important only at low temperatures. | It is the permanent deformation independent of time that occurs under stress, important only at high temperatures. | Chemistry | It is the time-dependent permanent deformation that occurs under stress, important only at high temperatures. | 83 | 3 | bcc8aeb5-48a3-47f1-9c65-87f2390a519d | 2021 |
What is a common way to prepare solutions of hypochlorite, a component of bleach?: | Mild oxidation of chlorine in a basic medium. | Mild oxidation of chlorine in an acidic medium. | Dismutation of chlorine in a basic medium. | Chemistry | Reduction of chlorates in a basic medium. | 84 | 4 | 3558a712-cba0-4e0d-a429-48fa1564a15d | 2021 |
In a complex of the type [ML6]n+, where the metal has 4 electrons in 3d orbitals, and L is considered a weak field ligand, how many electrons will be unpaired according to the crystal field theory? | 3. | 4. | 0. | Chemistry | 2. | 85 | 1 | 1459874d-d8a7-40b9-90ae-503cf39cb8bb | 2021 |
What conditions must the speed of light in two media meet for there to be refraction when a beam of light passes from one to the other? | That it be different in both media. | That it be equal in both mediums. | That it be smaller in the initial medium and larger in the end. | Chemistry | That it is greater in the initial medium and smaller in the end. | 86 | 2 | 444c89c0-d8d8-4905-8cd3-2343b4df6143 | 2021 |
How is the carbon suboxide C12O9 obtained? | Reducing CO with hydrogen. | Reducing the CO with sodium. | Dehydrating the benzenehexacarboxylic acid. | Chemistry | Burning coal with little oxygen. | 87 | 4 | e06bbca1-3281-44b9-b1f3-8682be4a2ae0 | 2021 |
The diamond, graphite, fullerenes, and carbon nanotubes are: | Allotropes of carbon. | Carbon Isomorphs. | Carbon Isomers. | Chemistry | Isotopes of Carbon. | 88 | 2 | 78fcffcd-79c1-4673-bce5-f3166bc66e34 | 2021 |
Which of the following metallic ions does not usually cause intense coloration in their coordination compounds?: | Zn2+. | Cu2+. | Fe2+. | Chemistry | Co3+. | 89 | 2 | 4f1bfb0a-58f7-471b-bcf8-71568745fd6f | 2021 |
Tin forms two chlorides, SnCl2 and SnCl4. Which of the following statements is true?: | Both compounds are covalent compounds. | Both compounds are ionic compounds. | The greater polarization capacity of Sn4+ (compared to Sn2+) makes SnCl4 an ionic compound. | Chemistry | SnCl2 is an ionic compound and SnCl4 is a covalent compound. | 90 | 3 | 0a5e87a0-b9e1-40c0-a0e8-c63b70100013 | 2021 |
Which of the following reactions at room temperature is the most violent?: | BF3 + HOCH3. | BF3 + H2O. | BI3 + H2O. | Chemistry | BCl3 + H2O. | 91 | 4 | 10d77493-b1cc-4047-9139-da738befdb14 | 2021 |
Group 12 of the Periodic Table contains the metals Zn, Cd, and Hg. Which of the following statements related to these three elements is false?: | Zn and Cd are very similar in their chemical behavior, but while Zn is an essential trace element (the second most important after iron), Cd is toxic to all living beings. | Zn, Cd and Hg should be considered transition metals as they belong to the d-block of the Periodic Table. | Mercury, which presents two states of oxidation: +2 (Hg2+) and +1 (Hg22+), is especially toxic in its organomercury forms (such as the methylmercury cation, HgCH3+). | Chemistry | The three metals, but especially mercury, tend to form covalent compounds in addition to ionic compounds. | 92 | 1 | a7e6b556-a37f-4d0c-9b61-8eb55413d467 | 2021 |
What is the term for the weak form of induced or non-permanent magnetism for which the magnetic susceptibility is negative? | Diamagnetism. | Paramagnetism. | Ferrimagnetism. | Chemistry | Ferromagnetism. | 93 | 2 | 5953a568-bfdc-4082-bfba-55611e6b41f0 | 2021 |
What is the highest oxidation state that Ruthenium and Osmium can achieve? | Seven. | Eight. | Four. | Chemistry | Six. | 94 | 1 | b949ac47-3632-437c-b8f3-08a26e5b7f91 | 2021 |
Which of the following compounds is insoluble in water?: | CaF2. | AgF. | CuBr2. | Chemistry | CuCl2. | 95 | 2 | c818a731-1cd9-4c09-8e6e-100630053e31 | 2021 |
Which of the following statements about Latimer diagrams is false?: | The species are connected by arrows and the numerical value of the standard reduction potential (at 25 ΒΊC and [species]=1M) is written (in volts) on each arrow. | The most oxidized species of the element is written on the left side, and to the right, successively the species with lower oxidation states. | They allow to identify those species that disproportion (or dismutate) spontaneously. This happens if the potential on the right side of the species is less than the potential found on its left side. | Chemistry | They contain enough information to be able to deduce the standard reduction potentials of non-adjacent species. | 96 | 4 | 8e449133-cce0-49cb-91ad-e70b455a1e5c | 2021 |
What term do we use to refer to the hydrogen molecule where the nuclear spins rotate in the same direction? | Para-hydrogen. | Ortho-hydrogen. | Tritium. | Chemistry | Deuterium. | 97 | 1 | cf0eea2c-8ab9-40f6-95b8-442490658870 | 2021 |
To which type of structure does the definition "Close cubic packing of anions, with cations occupying all tetrahedral voids" correspond? | Nickel arsenide. | Blende. | Antifluorite. | Chemistry | Fluorite. | 98 | 4 | aa234d8c-5130-4c53-8635-bff226e84b74 | 2021 |
Which of the following statements about Frost diagrams is false?: | The longer the straight line connecting two points on the diagram, the greater the oxidizing power of the oxidized form of the pair, which will tend to reduce. | Frost diagrams are constructed at 25 Β°C [species] = 1 M and can be for acidic environments, [H+] = 1 M and pH = 0, or for basic environments, [OH-] = 1 M and pH = 14. | Any species situated below the line connecting two adjacent species to the first is more stable than them and, therefore, in a mixture of these two species there occurs spontaneously a commensurability (or switching) of them to generate the stable species. | Chemistry | Any species positioned above the line that connects two adjacent species spontaneously dismutates into those two species. | 99 | 2 | dc9a20de-df41-4e41-9669-2f159c81fe46 | 2021 |
Which is the element with the highest number of allotropic forms? | Phosphorus. | Carbon. | Sulfur. | Chemistry | Oxygen. | 100 | 4 | d0d7eee3-4a79-4432-a553-926282890083 | 2021 |
Which of the following species is known as "slaked lime"?: | CaO. | CaCO3. | CaSO4. | Chemistry | Ca(OH)2. | 101 | 3 | d53d1f8d-fe27-4e98-a594-4e89545abffe | 2021 |
What is a hypoeutectoid alloy? | For a system with a eutectoid, the alloy for which the solute concentration is greater than the composition of the eutectoid. | For a system with a eutectoid, the alloy for which the solute concentration is less than the composition of the eutectoid. | For a system with a eutectoid, the alloy for which the solvent concentration is greater than the eutectoid composition. | Chemistry | For a system with a eutectoid, the alloy for which the concentration of the solvent is less than the composition of the eutectoid. | 102 | 1 | 37198b1c-f49e-4390-9460-5f92982bbad0 | 2021 |
The use of cobalt-60 in radiotherapy can be produced by bombarding cobalt-59 with: | Alpha particles. | Neutrons. | X-rays. | Chemistry | Beta particles. | 103 | 1 | fc4ff07e-cab0-42e6-b6cc-511da3e110c6 | 2021 |
What type of compounds is silver iodide a representative example of? | Superconductors. | Semiconductors. | Piezoelectrics. | Chemistry | Fast ionic conductors. | 104 | 3 | 082f6192-14d9-48c3-9338-a7ebd4ba3301 | 2021 |
What are the geometries adopted by the ML6 coordination compounds? | The octahedral and the trigonal prism. | The trigonal bipyramid and the trigonal prism. | The cubic and the octahedral. | Chemistry | The icosahedral and the octahedral. | 105 | 2 | 039b6214-fe2d-40ca-b496-a5d464ce646c | 2021 |
In the electronic ionization process of the mass spectrometer. When the kinetic energy of the electrons from the source is reduced, the following occurs: | Less fragmentation and greater abundance of the molecular ion. | Greater fragmentation. | The fragmentation is maintained and the molecular ion tends to disappear. | Chemistry | Less fragmentation and lower abundance of the molecular ion. | 106 | 2 | bc1d2377-e1e9-49cd-bfdc-506735642f68 | 2021 |
Which of the following statements is not true in a calibration procedure using the standard addition method? | The calibration curve should always be linear in the sample matrix. | A blank measurement is carried out so that foreign species do not contribute to the analytical signal. | It is usually used to correct signal losses due to sample preparation. | Chemistry | The complex interference effects due to the matrix are compensated. | 107 | 4 | facc2f14-cb42-4cbb-8f03-c5b0ad870ec9 | 2021 |
Accelerated solvent extraction (ASE) uses: | Organic solvents at high temperature and pressure for the extraction of organic compounds from solid samples. | High temperature and pressure inorganic solvents for the extraction of organic compounds from solid samples. | Polar organic solvents to favor the heating and extraction of organic compounds from solid samples. | Chemistry | Fluids at pressures and temperatures higher than the critical points to achieve the extraction of organic compounds from solid samples. | 108 | 2 | c754b4e4-643a-41dc-b660-cb5899dd6e16 | 2021 |
In the technique of reverse phase liquid chromatography: | The mobile phase is an organic solvent that is immiscible with water. | The stationary phase is more polar than the mobile phase. | The stationary phase has the same polarity as the mobile phase. | Chemistry | The stationary phase is non-polar and the mobile phase is polar. | 109 | 3 | 699b5c3a-75a6-4b4f-8d02-0cf6a7543590 | 2021 |
What is the oxidation half-reaction of the thiosulfate ion to tetrathionate by iodine? | 2S2O32- β S4O62- + 2e-. | 2S2O32- β S4O62- + 1e-. | 2S2O32- β S4O62- + 4e-. | Chemistry | 2S2O32- β S4O62- + 3e-. | 110 | 2 | 1433f010-f353-492a-9ce1-d211ee05e215 | 2021 |
Which of the following statements related to Beer's Law is not correct?: | Beer's Law only describes the behavior of the absorption of diluted solutions. | According to Beer's Law, absorbance is inversely proportional to the concentration of the absorbing species. | According to Beer's Law, absorbance is directly proportional to the path length of the light beam through the absorbing medium. | Chemistry | The Beer's Law can be used to calculate molar absorptivities of species if the concentration is known. | 111 | 1 | 98a8f4c7-5727-42d2-8fdb-d6c66b45b8d0 | 2021 |
It is desired to prepare 500 mL of a 0.1 M aqueous solution of reagent A. To do this, a commercial reagent with a concentration of 10 M is available. How many mL of this reagent should be diluted to 500 mL to prepare the requested solution? | 1 mL. | 0.1 mL. | 50 mL. | Chemistry | 5 mL. | 112 | 3 | ee6967f9-ad7d-4848-ad86-6368420231af | 2021 |
Size exclusion chromatography is a type of column liquid chromatography in which: | The compounds of smaller molecular size exit the column before those of larger size. | The compounds with larger molecular size come out of the column before those with a smaller size. | The elution of the compounds to be separated depends on the composition of the mobile phase. | Chemistry | The elution of the compounds to be separated depends on the polarity of the stationary phase. | 114 | 1 | 025e90db-fb5d-4f9f-81d7-b12bb8e63133 | 2021 |
Which of the following types of interferences does not correspond to the chemical interferences that can occur in Atomic Absorption Spectroscopy? | Presence of dissociation equilibriums. | Formation of low-volatile compounds. | Overlap of atomic lines. | Chemistry | Presence of ionization equilibriums. | 115 | 4 | 0635cbf0-869b-485a-a533-b22968cb58b8 | 2021 |
The efficiency of most chromatography columns can be approximated using the following expression H = Bu + Csu + CMu. What does the term Bu represent in the previous equation?: Note: u is the linear velocity of the mobile phase. | Plate height. | Longitudinal diffusion. | Number of plates. | Chemistry | Mass transfer in the mobile phase. | 116 | 1 | 99929617-c072-46e0-b975-06dc79384cd1 | 2021 |
The internal standard used in liquid chromatography coupled to mass spectrometry is used for: | Reduce the noise of the detector. | Promote the derivatization of the sample and obtain a higher signal. | Promote the ionization of the sample in the electrospray, avoiding ion suppression. | Chemistry | Reduce the variability associated with the process of sample preparation and injection. | 117 | 3 | 0c83747a-a445-414f-93ac-8feeb0333e39 | 2021 |
What does gradient elution consist of in Gas Chromatography (GS)? | The variation of the oven temperature during the analysis in a continuous and stepwise manner. | The division of the mobile phase flow before entering the chromatographic column. | The use of different mobile phases during the analysis. | Chemistry | The variation of the concentration of the mobile phase during the analysis in a continuous and staggered manner. | 118 | 2 | ae1572d6-6418-47cd-b256-60fdff6ab0cc | 2021 |
An analytical method is homoscedastic if: | The variance of the signal remains constant for different concentrations of analyte. | It provides the same signal for different concentrations of analyte as long as the same matrix is used. | When the concentration of analyte is zero (blank), the signal is zero. | Chemistry | The increase in signal is proportional to the analyte concentration throughout the entire linear range of measurement. | 119 | 2 | 8fdb58e0-4589-4a3b-a759-9023f0a77c6e | 2021 |
Regarding the deuterium lamp. Which of the following statements is correct?: | It emits wavelengths of the visible spectrum. | Emits in a continuous spectrum. | It emits in a spectrum of lines. | Chemistry | It emits in wavelengths of the visible spectrum and part of the infrared. | 120 | 1 | a9cea5b7-f22d-451f-b72e-f2370f219cc6 | 2021 |
In the separation of a protein mixture using affinity chromatography, which statement is correct?: | The larger the size of the protein, the greater its retention will be and it will be eluted at longer elution times. | The species with lower molecular weight are eluted in the exclusion volume (or dead volume). | It requires the existence of positively charged functional groups in the structure of the biomolecules to be separated. | Chemistry | The separation takes place based on a specific interaction between the proteins in the sample and specific recognition ligands attached to the stationary phase. | 121 | 3 | 86fe224b-4bae-41ab-83e3-002905780443 | 2021 |
In the neutralization reaction between sodium hydroxide and acetic acid, the pH of the resulting solution at the equivalence point is: | That of the buffer mixture. | Neutral. | Less than 7. | Chemistry | Greater than 7. | 122 | 3 | 1b8c9771-d025-4c4c-bba4-0dc584961a0e | 2021 |
Which of the following statements about the influence of ππ²π on the titration of a weak acid with a strong base is correct: | The smaller the value of ππΎπ of the acid, the greater the pH change in the region of the equivalence point. | The higher the ππΎπ value of the acid, the greater the pH change in the equivalence point region. | The magnitude of the pH change in the equivalence point region does not depend on the ππΎπ of the acid. | Chemistry | The lower the value of ππΎπ of the acid, the smaller the change in pH in the region of the equivalence point. | 123 | 2 | 74769ffb-60dd-420b-bfe7-0668468e5671 | 2021 |
Which of the following parameters is not related to the thermal noise of an analytical instrument?: | The temperature. | The resistance. | The bandwidth of frequency. | Chemistry | The current intensity. | 124 | 3 | e1de9fc2-8fdc-45e6-a75c-730ec92e101e | 2021 |
If we have a solution containing an acid π―π¨ (ππ²ππ = π) with an initial concentration of 0.20 M and we set the pH=5, what will be the concentration of the base A-? | 0.10 M. | 0.05 M. | 0.50 M. | Chemistry | 0.20 M. | 125 | 2 | 7584a7d2-35c3-46c5-bc06-35b0a57a75e4 | 2021 |
The resolution in high performance liquid chromatography increases: | Increasing the volume of the sample introduced into the chromatographic system. | By decreasing the length of the chromatographic column. | When reducing the size of the homogeneous particle packed in the chromatographic column. | Chemistry | When using very low mobile phase speeds. | 126 | 4 | 58c5a741-af71-4d15-b1c6-abc6368db4cd | 2021 |
What are the most suitable precipitates for a gravimetric determination? | The precipitates formed by large particles. | The precipitates formed by colloids. | The precipitates formed by nanoparticles. | Chemistry | The precipitates formed by small particles. | 127 | 2 | afb432fa-035a-4b1e-85e7-13ca0e208365 | 2021 |
In molecular fluorescence spectroscopy: | The value of the quantum yield of fluorescence is inversely proportional to the concentration of the luminescent molecule. | The quantum yield of fluorescence decreases, in most molecules, when the temperature is lowered. | The fluorescent emission is favored in molecules that possess rigid structures. | Chemistry | After the absorption of radiation, the emission of photons with a shorter wavelength than those that were absorbed occurs. | 128 | 4 | b113c9b0-5c91-45b6-b5e5-a1fe8202ebc4 | 2021 |
What type of cuvette is used to determine the molecular absorption of a compound at a wavelength of 250 nm? | Sodium chloride bucket. | Plastic bucket. | Glass cuvette. | Chemistry | Quartz cuvette. | 129 | 3 | 8059c59d-f93e-43e9-a1a4-53b6e12ad170 | 2021 |
What is the endpoint of the titration of oxalic acid with potassium permanganate? | When the first purple hue appears in the solution. | When the first green hue appears in the solution. | When the initial purple hue in the solution disappears. | Chemistry | When the initial yellow hue disappears in the solution. | 130 | 2 | e3d3b8a9-a8a4-4570-a0f0-949b4f94c8e3 | 2021 |
What is the appropriate pH range for measurements with a fluoride ion selective electrode? | 2 < pH < 4. | 1 < pH < 2. | 9 < pH < 13. | Chemistry | 5 < pH < 8. | 131 | 3 | 73821a85-df46-439c-89e0-202b0fe7c77b | 2021 |
Which of the following statements corresponds to isobaric interferences in Inductively Coupled Plasma Mass Spectrometry? | These are interferences produced by elements that possess isotopes whose mass is the same as that of the analyte to be determined. | These are interferences that occur due to the high pressures that are generated in the nebulizer when introducing the sample. | They are due to the presence of polyatomic species whose masses coincide with that of the isotope of the analyte to be determined. | Chemistry | These are interferences that occur due to the ionization of the element. | 132 | 2 | 854c5bb2-c2a1-490b-b707-ad7732c9781a | 2021 |
Which of the following detectors is used in Mass Spectrometry?: | Charge Coupling Detector. | Continuous dynode electron multiplier. | A bolometer. | Chemistry | Charge transfer detector. | 133 | 1 | a6369957-ff40-4047-a495-1a487b6c013d | 2021 |
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