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Nitriles are hydrolyzed to: | Amines. | Aldehydes. | Carboxylic acids. | Chemistry | Ketones. | 127 | 4 | 0aad6acb-9e01-4237-a6ba-fffadfd13352 | 2023 |
The structure of furan is analogous to that of pyrrole, except that the NH has been replaced by an: | C. | S. | P. | Chemistry | O. | 128 | 3 | 2396dc79-51ba-405b-bc53-3ee943fe33c4 | 2023 |
The fusion of a benzene ring in positions 2,3 of a pyrrole generates: | Isoquinoline. | Quinoline. | Indole. | Chemistry | Quinidine. | 129 | 4 | 67dd48b4-4f22-4994-b805-a0a63bdd9a94 | 2023 |
Indicate which of the following cations is more stable: | CH3–CH2+. | CH3+. | CH2=CH–CH2+. | Chemistry | (CH3)2CH+. | 131 | 4 | 197367ab-df10-4ac3-8162-351c3f1dac11 | 2023 |
What product/s will result from treating (E)-3-hexene with Br2? | A mixture of diastereomeric dibromides. | A mixture of enantiomeric dibromides. | A meso dibromide. | Chemistry | (E)-3,4-dibromo-3-hexene. | 134 | 4 | 32444e22-5446-4734-9f6b-2cc8b90f44d7 | 2023 |
Which of the following statements, about the heterocycle pyridine, is false?: | The reaction of pyridine with acetic acid yields pyridinium acetate. | Pyridine is a stronger base than pyrrole. | Pyridine is a stronger base than piperidine. | Chemistry | Pyridine is deactivated towards electrophilic attack, but it is activated towards aromatic nucleophilic substitution. | 135 | 4 | dce68f04-38bb-4007-b14c-de888a78f109 | 2023 |
What is the name of the reaction by which, in the presence of a strong base, primary amides react with chlorine or bromine to form amines with one less carbon atom? | Curtius Rearrangement. | Gabriel Synthesis. | Sandmeyer Reaction. | Chemistry | Hofmann Rearrangement. | 136 | 3 | 0af52935-336f-4560-88e6-5f3db90e228b | 2023 |
The 2-butanol can be obtained from propyne through the following sequence of reactions: | 1. NaOH; 2. CH3Br; 3. H2/cat. Lindlar; 4. H+/H2O. | 1. NaNH2; 2. CH3Br; 3. H2/cat. Lindlar; 4. H+/H2O. | 1. NaNH2 ; 2. CH3CH2Br ; 3. H2/cat. Lindlar ;4. H+/H2O. | Chemistry | 1. NaNH2 ; 2. CH3Br ; 3. H2/Pd-C; 4. H+/H2O. | 137 | 1 | c485f13b-79f7-40f4-9659-8d399643ca7f | 2023 |
What is the major product obtained when ethyl acetoacetate is treated with an excess of sodium borohydride in methanol? | 1,3-butanediol. | Methyl 3-hydroxybutanoate. | 4-hydroxy-2-butanone. | Chemistry | 3-oxobutanoic acid. | 139 | 1 | 6d47f992-f551-4613-a21e-f0d932f8f177 | 2023 |
Which of the following statements is true?: | Grignard reagents are electrophilic reagents in their reaction with ketones. | The reaction between a ketone and a Grignard reagent is irreversible because carbocations are poor leaving groups. | The reaction between a ketone and a Grignard reagent is irreversible because carbanions are poor leaving groups. | Chemistry | Ketones are nucleophilic reagents in their reaction with Grignard reagents. | 141 | 4 | 3dfaa177-bb92-4ba0-bbac-1f3c21dc027d | 2023 |
Which of the following bases is most suitable for carrying out the transformation of 2-bromo-3-methylbutane into 2-methyl-2-butene?: | Pyridine. | KOCH3. | Lithium diisopropylamide. | Chemistry | KOC(CH3)3. | 143 | 1 | ac51ded8-e3a0-46c9-8404-800c66391dc3 | 2023 |
What is the descending order of nucleophilicity, in hydroxylic solvents, of the following species: water, methoxide ion, triethylphosphine, and acetate ion? | Triethylphosphine > methoxide ion > acetate ion > water. | Methoxide ion > acetate ion > triethylphosphine > water. | Acetate ion > methoxide ion > triethylphosphine > water. | Chemistry | Triethylphosphine > acetate ion > methoxide ion > water. | 144 | 2 | 785d57dd-1a1c-418c-b513-9b69009bdc4a | 2023 |
Which of the following statements about tautomerism is false?: | Tautomers are resonant forms. | Tautomers are isomers that interconvert. | Tautomerism occurs due to the migration of a proton and the movement of a double bond. | Chemistry | Tautomers are different compounds. | 146 | 2 | d99133cd-6111-436f-a73d-6b2f65a04a4b | 2023 |
What is the majority organic product obtained in the reaction of 2-methylpropanal with sodium hydroxide at 5ºC? | 2-methylpropanoic acid. | 2-methylpropanol. | 2,3,4-trimethylpentanal. | Chemistry | 3-hydroxy-2,3,4-trimethylpentanal. | 147 | 3 | 4dc7e870-2127-4229-b09b-330239c6f3fa | 2023 |
Which of the following statements is false?: | The metathesis reaction with ring opening of cyclic alkenes is usually carried out with Grubbs' reagent. | The metathesis reaction with ring opening of cyclic alkenes gives rise to dienes. | The ring-opening metathesis reaction of cyclic alkenes can be carried out in the presence of other functional groups. | Chemistry | The metathesis reaction with ring opening of cyclic alkenes leads to the formation of ethylene. | 149 | 3 | a25822d8-ff7b-4efe-bc35-460747a06ee8 | 2023 |
Which of the following techniques is not suitable for separating the enantiomers of a racemic mixture of thalidomide?: | Distillation. | Chiral chromatography. | Reaction with chiral resolution agents. | Chemistry | Crystallization. | 150 | 2 | 9f328290-13c5-41f1-8561-44bda0c290c0 | 2023 |
The general formula of an acyclic hydrocarbon with two triple bonds is: | CnH2n–6. | CnH2n-4. | CnH2n–10. | Chemistry | CnH2n-2. | 151 | 2 | fb45ea2c-a428-4d6f-99fd-62c1fa8b7b52 | 2023 |
What is the phrase that best describes the mechanism of nucleophilic substitution in a tertiary halide?: | Concerted reaction with retention of configuration. | Formation of a carbocation with retention of configuration. | Formation of a carbocation with partial racemization. | Chemistry | Concerted reaction with inversion of configuration. | 152 | 4 | 0df8ab35-23a0-4583-a731-403194733504 | 2023 |
What product would be obtained by treating 2,3-dimethyl-2,3-butanediol with H2SO4, at 100ºC? | 2,3-dimethyl-1,3-butadiene. | 3,3-dimethyl-2-butanone. | Acetone (2 equivalents). | Chemistry | 1,1,2,2-tetramethyloxirane. | 153 | 1 | ec986a84-7a4f-430a-964d-d800e8e7b007 | 2023 |
What product is obtained by heating 1,3-butadiene with acrylonitrile (CH2=CH–C≡N)? | 3-cyclohexene-1-carbonitrile. | 4-vinylcyclohex-1-ene. | 6-vinyl-2,5-dihydropyridine. | Chemistry | 3-vinylcyclobutane-1-carbonitrile. | 154 | 2 | 4e0e60c1-32f2-402e-890b-ac41ddfb4d55 | 2023 |
Which of the following pi cyclic systems is aromatic?: | Cyclopropenyl cation. | Cyclooctatetraene. | Cyclopentadienyl cation. | Chemistry | Cyclopropenyl anion. | 155 | 2 | d856d0df-5f72-4f46-8a1e-9dec95afa23d | 2023 |
What type of predominant organic compound would you expect in the reaction of cyclohexanone with methylamine in the presence of sodium cyanoborohydride in ethanol? | A hydroxylamine. | A nitrile. | An imine. | Chemistry | An amine. | 156 | 3 | 5a3bb4b4-7a68-4490-aac8-8498fd90910c | 2023 |
The compound (R,R)-1,2-dibromocyclobutane: | It is an optically inactive compound. | It has two asymmetric carbons and is therefore a chiral compound. | It has no asymmetric carbons and is therefore an achiral compound. | Chemistry | It is a meso compound and therefore an achiral compound. | 157 | 1 | 591e7e2f-fcee-47a8-9fcb-36843c95544f | 2023 |
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, the reaction being faster if starting from the cis isomer of the starting substance. | Chemistry | The compound 4-(1,1-dimethylethyl)cyclohex-1-ene is produced, with the reaction being quicker if starting from the trans isomer of the starting substance. | 158 | 4 | 89293250-c460-45bf-b440-977c023465ec | 2023 |
Which of the following statements, related to acetals, is false?: | Aldehydes form acetals faster than ketones. | The formation of acetals is catalyzed only by acids, but hydrolysis requires basic conditions. | Ethylene glycol is often used to prepare cyclic acetals. | Chemistry | The formation of an acetal does not alter the oxidation state of the carbon atom of the precursor carbonyl group. | 159 | 1 | f57ee15c-dd9e-42f7-be46-1c82dd9eabf5 | 2023 |
Which of the following statements is correct for glycosphingolipids?: | Its main function is energy storage. | They are nonpolar. | They have two fatty acid residues in their molecule. | Chemistry | In the event they carry sialic acid, they are called gangliosides. | 160 | 3 | d4dd0f35-754c-48c4-81c6-6482103644de | 2023 |
Which of the following statements is true for the oxidation of fatty acids?: | It takes place in the cytosol. | The oxidation and synthesis of fatty acids occur with the same reactions, but in the opposite direction. | Fatty acids must be activated (by binding to CoA) to allow their internalization into the mitochondria. | Chemistry | It occurs with low plasma levels of glucagon or adrenaline. | 161 | 4 | e15d6c72-1e53-436c-a6e7-feeac8ffde14 | 2023 |
Which of the following statements is true for the nitrogen metabolism of amino acids?: | The first step in nitrogen elimination is usually the transfer of the αamino group to α-ketoglutarate. | Nitrogen is released in the digestion process by pancreatic proteases. | Transamination reactions are highly irreversible. | Chemistry | Aminotransferases are nonspecific and act on all amino acids. | 162 | 2 | c51102e7-04d2-498d-877e-e03bd021a8b0 | 2023 |
Which of the following statements is false for the synthesis of deoxyribonucleotides?: | The source of reducing equivalents is NADPH + H+. | The key enzyme is ribonucleotide reductase. | They are directly synthesized from deoxyribose. | Chemistry | The dATP allosterically inhibits synthesis. | 163 | 4 | 3e57ddfd-4186-4dc2-a9ff-ccc92a93e6b6 | 2023 |
The pKa values of aspartic acid are 2.1; 3.9 and 9.8. Its isoelectric point (pI) is: | 5.3 | 7.0 | 3.9 | Chemistry | 3.0 | 165 | 3 | a8c22b6b-3fcc-4147-91d2-c852fc451f07 | 2023 |
Proteins intended to be secreted are synthesized in: | The rough endoplasmic reticulum. | The free polysomes. | The smooth endoplasmic reticulum. | Chemistry | The Golgi apparatus. | 166 | 2 | 1573b32d-4cca-40a1-b13c-00c0afd3a98d | 2023 |
Squalene is a precursor of: | Prostaglandins. | Sphingosine. | Cholesterol. | Chemistry | Arachidonic acid. | 167 | 4 | 98fc6060-3328-4864-8a6e-5b1bd4cfb767 | 2023 |
Each fatty acid oxidation cycle: | It uses up two molecules of NADH. | Releases a molecule of acetyl-CoA. | It causes dehydration. | Chemistry | It generates two molecules of FADH2. | 168 | 1 | c8796c36-dc77-44cf-a206-cc095739c1ef | 2023 |
The malate-aspartate shuttle: | It serves to transfer the electrons from NADH in the cytosol to the mitochondria. | It allows the regeneration of cytosolic NADH necessary for glycolysis. | It is an electron transport complex. | Chemistry | Transfer the electrons from NADH to citrate. | 169 | 2 | 0dac7e02-05d9-430c-931c-354e9359f44d | 2023 |
Regarding the Michaelis-Menten constant (Km): | A high value of Km can be related to great stability of the enzyme-substrate complex. | It is expressed in units of speed. | It remains constant for enzymes of the same class. | Chemistry | It equates to the substrate concentration required to reach half of the maximum speed. | 170 | 3 | 5a8e9dff-4e80-45cb-bdf1-10fc7be8e5a3 | 2023 |
What wavelength would be strongly absorbed by a red colored solution? | 585 nm. | 450 nm. | 650 nm. | Chemistry | 600 nm. | 171 | 1 | 1c5b1ddc-56e9-4f40-8600-b83c1094c91f | 2023 |
Which of the following biochemical processes is promoted by insulin?: | Gluconeogenesis. | Glycogenolysis. | Uptake of glucose by cells. | Chemistry | Lipolysis. | 172 | 4 | c1d515c1-634e-4dfb-b95e-df7e99206bcd | 2023 |
The electrophoretic movement of proteins towards the anode decreases when it is increased: | The ionic strength of the buffer. | The pH of the buffer. | The voltage. | Chemistry | The intensity of the current. | 173 | 2 | 05a85886-11bd-4d17-ba82-8e646bc28463 | 2023 |
Restriction endonucleases: | 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 sequences free of nucleosomes. | Chemistry | They recognize and cut the DNA in specific sequences. | 174 | 3 | 8137317c-f735-4576-a666-1c28fdb39e48 | 2023 |
Enzymes alter: | Reaction rates but not equilibria. | Reaction rates and equilibrums. | The affinity for substrates. | Chemistry | Only the balances of the reaction. | 175 | 2 | 79a539a6-0f08-4ef7-89a6-957588698a11 | 2023 |
The polymerase chain reaction allows: | Amplify specific DNA sequences. | Mapping and identifying the genes of a genome. | Locate structures in RNA sequences. | Chemistry | Understand the topology of specific DNA sequences. | 176 | 2 | 167a8346-8a79-45bc-9652-63fdc57d7eb8 | 2023 |
Topoisomerases are enzymes: | That allow the hybridization between two topological isomers of DNA. | That denature the double helix structure of DNA. | That they have helicase-primase activity. | Chemistry | That increase or decrease the degree of DNA unwinding. | 177 | 3 | 88194ab5-0c0c-44f3-8170-e65b558482c2 | 2023 |
The proofreading activity of prokaryotic DNA polymerase I is an activity: | 5'-3' Transesterification. | 5´-3´ Polymerizing. | 3'-5' Exonuclease. | Chemistry | 5' to 3' Exonuclease. | 178 | 4 | 771673f0-f79b-4342-b4d5-581c832eacd0 | 2023 |
About Vitamin B12: | Participates in carboxylation reactions. | It is also known as pyridoxine or pyridoxal. | It contains manganese in its structure. | Chemistry | Its activity is linked to that of folic acid. | 179 | 3 | 5d02ae32-3c57-473d-94b3-a3a067576104 | 2023 |
Which of the following amino acids is abbreviated with an E in the one-letter nomenclature? | Glutamic acid. | Aspartic acid. | Glutamine. | Chemistry | Asparagine. | 180 | 2 | c520b90a-e45b-472a-b9e4-db0247479e7c | 2023 |
In molecular biology, what is the temperature called at which half of the copies of a DNA sequence are in the form of a single strand and the other half are in the form of a double strand? | Conjugation temperature. | Hybridization temperature. | Melting temperature. | Chemistry | Transformation temperature. | 181 | 4 | 490abb4d-7235-46f4-8208-d411c1e4e2da | 2023 |
This is true in relation to euchromatin: | It is transcriptionally active. | It is very condensed. | Contains highly repetitive DNA sequences. | Chemistry | It constitutes 90% of the total chromatin. | 182 | 2 | 0fdba93f-478f-4795-b63b-12ea4de4c0ac | 2023 |
Indicate the incorrect statement regarding the Krebs Cycle: | It plays a crucial role as a link between the different metabolic pathways. | It generates two GTP molecules. | It is an amphibolic pathway. | Chemistry | It provides precursors for many biosynthetic pathways through its intermediates. | 184 | 1 | 476719ec-3545-4f97-a79b-6da81446538b | 2023 |
Which of the following amino acids contains sulfur?: | Methionine. | Leucine. | Proline. | Chemistry | Tryptophan. | 185 | 2 | ffd23fef-5afe-4a15-9a6c-1df81f976904 | 2023 |
Which of the following statements about the beta-sheet structure of proteins is not true?: | It is stabilized through hydrogen bond bridges. | The chains can only be arranged in a parallel manner, that is, in the same direction. | It is a type of secondary structure that is widely spread. | Chemistry | The side chains are arranged either above or below the plane. | 186 | 1 | 912a6135-0781-4a1b-ae2c-599d694f0006 | 2023 |
In the kinetics of an enzyme, competitive reversible inhibitors: | Both the Km and the Vmax decrease. | They reduce the Km without altering the Vmax. | They increase the Km without modifying the Vmax. | Chemistry | They increase the Km and decrease the Vmax. | 187 | 4 | b23e683b-679f-41e5-9234-0f2838735499 | 2023 |
The Krebs cycle or citric acid cycle is favored by high cellular concentrations of: | ADP and NAD+. | ATP and NADH. | ATP and NAD+. | Chemistry | ADP and NADH. | 189 | 2 | a0227cf1-d1dd-4593-841e-88ca6092a5d1 | 2023 |
In reference to vitamins, indicate the correct answer: | Excessive supplementation of biotin can cause ataxia and sensory neuropathy. | The function of thiamine is to transfer units of a carbon atom in the synthesis processes of RNA and amino acids. | A deficiency of pyridoxine can cause pellagra. | Chemistry | Vitamin C is involved in the formation of hydroxyproline in collagen. | 190 | 3 | cc961e72-38fe-4195-9564-c1f3b0fb2dbf | 2023 |
Regarding erythropoietin, indicate the correct answer: | It inhibits the production of red blood cells in the bone marrow. | It is a lipoprotein synthesized at the renal level. | Increases in progressive renal failure. | Chemistry | The tubular renal cells release it when the oxygen pressure decreases. | 191 | 3 | 7ed6d347-5442-4da6-82fb-d5cddad8b1fb | 2023 |
At the isoelectric point of amino acids and proteins: | The net charge of each ionizable group is zero. | Both ionizable groups of the amino acid have the same charge. | The charge is the same for all amino acids at a certain pH. | Chemistry | The algebraic sum of the charges of the ionizable groups is zero. | 192 | 3 | 2e524b34-6d62-4d5a-b43a-bb78b1e968d0 | 2023 |
If in a double-stranded DNA there is a 20% mole of guanine, what is the mole percentage of thymine?: | 30%. | 20%. | It cannot be known with that only piece of information. | Chemistry | 80%. | 193 | 2 | 3f8dbe84-824e-43c0-bb68-e7ef24f998db | 2023 |
The high fidelity of the protein synthesis process is primarily due to: | The presence of initiation and elongation factors specific for each aminoacyl-tRNA. | The activity of the peptidyl transferase enzyme. | The corrective activity of the aminoacyl-tRNA synthetase. | Chemistry | The coupling between the ribosome and the transfer RNA. | 194 | 4 | a35f5d40-80f1-4918-b7a3-75be46e10354 | 2023 |
Genetic imprinting (imprinting) is the: | Absence of certain genes in the genome. | Differential expression of one of the alleles. | Presence in the genome of genes that allow individual identification. | Chemistry | Expression of genes causing diseases. | 195 | 1 | 5cc86048-c0a0-4fd9-8ac2-269113792383 | 2023 |
Steroid hormones act at the cellular level: | Through the formation of a second messenger. | Inhibiting pre-existing enzymes. | Modifying the concentration of intracellular ionic calcium. | Chemistry | Through the regulation of gene expression. | 196 | 3 | 6c2e5ee5-28be-40a3-8a88-c8f34a9bf114 | 2023 |
In reference to the Klenow fragment, indicate the false statement: | Its great advantage is its stability at high temperatures. | It is a fragment of the enzyme DNA polymerase I. | It has polymerase activity and 3´→5´ exonuclease activity. | Chemistry | It is used for the filling of 3´ ends of DNA fragments. | 197 | 2 | e748a763-1527-4cc4-b636-a2de83baf0b2 | 2023 |
What is the Shine-Dalgarno sequence? | A sequence located 6 or 7 nucleotides from the termination codon of RNA translation. | A messenger RNA sequence that only exists in prokaryotes. | Sequence located 25 nucleotides from the transcription start site. | Chemistry | A consensus DNA sequence in the promoter region of eukaryotic genes. | 198 | 1 | 0c68f2c8-f840-4f7c-94dd-87812cfb7c36 | 2023 |
How does the increase in temperature affect the antigen-antibody reaction? | It reduces the speed and increases the binding affinity. | Increases speed and decreases binding affinity. | Decreases the speed and binding affinity. | Chemistry | Increases the speed and binding affinity. | 199 | 1 | 0e5fc49a-5889-47b2-96a0-432ef464802c | 2023 |
Plasmids are: | Double-stranded RNA molecules and circular with antibiotic resistance genes. | Linear DNA fragments with antibiotic resistance genes. | Circular DNA molecules that replicate independently of the host chromosome. | Chemistry | Circular DNA molecules that replicate in a chromosome-dependent manner of the host. | 200 | 4 | d26a110e-b4e1-46f0-8ee4-9833ebae03ee | 2023 |
Which of the following statements about Pourbaix diagrams is false?: | The more oxidized species are found in the upper part of the diagram, while the more reduced species are found in the bottom part. | These are graphical representations of the potential (ordinate) as a function of pH (abscissa) for a given element under standard thermodynamic conditions (usually water at 25°C). | Two oblique and parallel lines, which represent the oxidation of water (lower line) and the reduction of water (upper line), delimit a zone of the diagram that contains the stable species in aqueous solution. | Chemistry | The oblique lines indicate reactions between species dependent on both potential and pH. | 201 | 4 | a3562641-2dcf-4e02-856a-1c42a02976be | 2023 |
Which of the following compounds will undergo a rearrangement when subjected to a solvolysis reaction?: | 3-iodohexane. | 3-iodo-5-methylhexane. | 3-iodo-3-methylhexane. | Chemistry | 3-iodo-2-methylhexane. | 202 | 3 | 68d72fa7-10aa-4023-8a09-a98b394a0222 | 2023 |
What does the Mohs scale measure?: | Conductivity. | Acidity. | Viscosity. | Chemistry | Hardness. | 203 | 3 | 3b8f4c4a-6528-49b8-9b05-4f5559c85a76 | 2023 |
Bilirubin is: | A biomarker of kidney function. | A liver function biomarker. | A biomarker of brain function. | Chemistry | A biomarker of cardiac function. | 204 | 1 | 987d6baf-a015-46e7-b3a2-4ef05cd5fc8f | 2023 |
What type of capillary electrophoresis uses a continuous and stable pH gradient? | Capillary Gel Electrophoresis (CGE). | Capillary Zone Electrophoresis (CZE). | Capillary Isoelectric Focusing (CIEF). | Chemistry | Capillary Isotachophoresis (CITP). | 205 | 4 | bb34c60b-f789-44a4-9cd0-8518293a4a2f | 2023 |
What does the UFI code, which is mandatory on the label of products classified for their health risks, correspond to? | QR Code that includes information about the batch and expiry date of a product. | Alphanumeric code that allows the unique identification of a product during an emergency call to a toxicology center. | QR code that allows for the unique identification of a product during an emergency call to a poison control center. | Chemistry | Barcode that includes information about the batch and expiration date of a product and allows it to be identified during an emergency. | 206 | 1 | 0e8cf449-a695-4b23-ad01-7fc6d3a3784b | 2023 |
Molecular fluorescence: | It becomes more intense as the viscosity of the solvent decreases. | It becomes more intense as the temperature increases. | It exhibits a higher quantum yield of emission in mediums with elevated levels of oxygen. | Chemistry | It is particularly favored in rigid molecules. | 207 | 3 | b348ca76-7175-4fdc-a50e-cae4fa389392 | 2023 |
Consider the following reaction: C(s) + H2O(g) ⇌ CO(g) + H2(g). At equilibrium at a given temperature, the concentrations are: [H2O]=0.12 M and [CO]=[H2]=1.2 M. If all these concentrations increase by 0.5 M simultaneously, which of the following responses is true?: | More products will be formed. | More H2O(g) will be formed. | The value of Kc does not change, therefore, nothing happens. | Chemistry | It is necessary to know the value of Kp to understand what is happening. | 208 | 2 | fb7ba7f8-24f2-4650-8ff6-bf7b03a37a10 | 2023 |
Every measurement carries an associated error. Systematic errors are those produced by measuring equipment or by analysts who: | They always occur in the same direction, causing a bias. | Corrections are made by performing a large number of measurements. | They are due to chance and cannot be eliminated, although they can be minimized. | Chemistry | They cannot be corrected. | 209 | 2 | 438ad76d-dfa8-43ba-be3e-f4d6f23237ee | 2023 |
What is the enzyme responsible for unwinding the double helix during the DNA replication process? | DNA gyrase. | Primase. | DNA polymerase. | Chemistry | DNA helicase. | 210 | 3 | 381842ed-2235-4372-a3f9-54cf800595b5 | 2023 |
What is the process called in which hydrogen sulfide present in natural gas is removed, producing sulfur? | Claus Process. | Frasch Process. | Lead chamber process. | Chemistry | Kroll Process. | 1 | 2 | 54612900-f392-446f-bb88-3dd93805ab1f | 2022 |
The most stable allotrope form of elemental phosphorus is: | Red phosphorus. | White phosphorus. | Black phosphorus. | Chemistry | The violet phosphorus. | 2 | 4 | 0261a4a0-4856-4928-865d-e1508965662d | 2022 |
Is it possible to obtain any compound in oxidation state 8? | No, but it can reach oxidation state 7, for example OsF7. | Yes, for example, the OsO4 and the RuO4. | No, but it can reach oxidation state 7, for example OsBr7. | Chemistry | No, but oxidation state 7 can be achieved, for example OsCl7. | 3 | 1 | fab5715a-6618-4b27-9299-edd1a4d06892 | 2022 |
Which of the following statements about ionic compounds is false?: | They have high melting points. | All ionic compounds are solids and their crystals are hard and brittle. | Almost all dissolve in very polar solvents (like water) generating solutions that conduct electricity. | Chemistry | If they do not decompose when heated, in a melted state they act as insulators. | 4 | 3 | 81fbb51f-f137-4f8e-9ea3-20d7b996265e | 2022 |
With which elements does fluorine form compounds? | With all except the noble gases. | With all except He, Ne and Ar. | With all except the other halogens. | Chemistry | With all except the alkalines. | 5 | 1 | b6c9da20-6362-4164-954e-657730e835f5 | 2022 |
What is optical fiber?: | Ultra high purity thin silica fiber. | Ultra high purity thin iron oxide fiber. | Thin silica fiber with aluminum oxide impurities. | Chemistry | Thin fiber of iron oxide with impurities of manganese oxide. | 6 | 2 | 6ca8eb2d-7080-4076-94d6-ee68775588c8 | 2022 |
The thiosulfate anion was widely used in photography, it is very commonly used as a reducer and has various uses in Medicine. What is its formula? | S2O32- | S4O62-. | S2O72-. | Chemistry | HSO3-. | 7 | 2 | 02758be5-efb4-4719-be41-374af41c1830 | 2022 |
Cobalt: | In its metallic form, it has no magnetic properties. | It is a soft metal with a metallic color. | It is an essential element for living beings. | Chemistry | It is very reactive as a chemical element. | 8 | 4 | 7eba0f1e-9c36-472f-94e1-47aa658fbc4a | 2022 |
What type of defect is a Schottky defect? | Intrinsic point defect. | Extrinsic point defect. | Linear defect. | Chemistry | Extended defect. | 9 | 2 | baeb8402-2825-4b40-8359-7991a582d5e5 | 2022 |
Which of the following reactions requires a catalyst to be fast? | H2O2 (liquid) + SO2 (gas) → H2SO4. | H2O2 (liq.) → H2O (liq.) + ½ O2 (gas). | Cl2 + 2 NaOH → NaCl + NaClO + H2O. | Chemistry | NO (gas) + ½ O2 (gas) → NO2 (gas). | 10 | 1 | 3c6083dc-35e6-405a-8684-9c91337960b1 | 2022 |
For which of the following elements is the tetrafluoride unknown?: | Pr. | Ce. | Tb. | Chemistry | Eu. | 11 | 3 | 001a66cc-d92a-4fd6-9759-ac8917b1d48f | 2022 |
Mercury exists in nature mainly as cinnabar, HgS. Its formation can be interpreted as an acid-base reaction. What type of reaction is it? | The anion is a soft base that reacts with the soft acid cation. | The anion is a hard base that reacts with the hard acid cation. | The anion is a soft acid that reacts with the soft base cation. | Chemistry | The anion is a soft base that reacts with the hard acid cation. | 12 | 2 | 5c8ae19d-6b61-4a34-b1c0-13c6a7e17883 | 2022 |
What is the most abundant metallic element by mass in the human body? | Sodium. | Magnesium. | Calcium. | Chemistry | Potassium. | 13 | 4 | 26c6d59f-9fa6-49f6-b742-185c51efc43e | 2022 |
For the following pairs of chemical species, in which case are both species diamagnetic? | 29Cu+ and 28Ni. | 29Cu+ and 30Zn2+. | 29Cu2+ and 28Ni2+. | Chemistry | 30Zn2+ and 28Ni. | 14 | 1 | 09eb4bdf-c3bb-4ef6-bbaf-a1f783013570 | 2022 |
What is the idealized formula of apatite? | Ca10(PO4)6X2, (X: OH, Cl or F). | Ca10(PO4)6X4, (X: OH, Cl, or F). | Mg10(PO4)6X3, (X: OH, Cl or F). | Chemistry | Ca10(PO4)5X2, (X: OH, Cl or F). | 15 | 2 | e168e25a-311b-48d9-8948-6fa930d13bf3 | 2022 |
Which metal does the dinitrogen molecule, N2, react with at room temperature? | With iron. | With lithium. | With lead. | Chemistry | With tungsten. | 16 | 1 | 745abc4b-22a6-44d3-bb3d-6a461f4d2c0f | 2022 |
If ammonium nitrate (or ammonium nitrate) is considered, it can be affirmed that: | Both the nitrate anion and the ammonium cation have tetrahedral structures. | It has no industrial/agri-food utility. | It decomposes into N2, O2 and H2O when heated at low temperature, but into N2O if done at high temperature. | Chemistry | It is a hygroscopic compound (it absorbs moisture to form a sticky mass that hardens when the humidity drops) and at the same time a powerful explosive. | 18 | 3 | d85ee5ee-f753-4c86-a205-c5e56fcc3cce | 2022 |
The temperature above which a ferromagnetic material stops behaving as such and begins to behave as a purely paramagnetic material is called: | Planck Temperature. | Curie Temperature. | Rankine Temperature. | Chemistry | Néel Temperature. | 19 | 1 | dd9c13cb-34f6-4cf7-8d4d-927a30c0bb88 | 2022 |
What is the result of the reaction of H2S with SO2 at 300º C in the presence of iron oxides? | H2S + 2 SO2 → H2S3O4. | H2S + SO2 → S2O + H2O. | 2 H2S + SO2 → 3/8 S8 + 2 H2O. | Chemistry | H2S + 3 SO2 → H2S4O6. | 20 | 4 | 71f08fce-281b-4f16-964a-419dd0adedd7 | 2022 |
What type of carbide is WC? | Covalent carbide. | Ionic carbide. | Saline carbide. | Chemistry | Interstitial carbide. | 21 | 3 | 222253e0-44b4-44e7-9cd3-179a4e53409e | 2022 |
Hydrogen chloride: | It is extremely soluble in water, being able to generate concentrated solutions that contain approximately 38% of the acid by mass, a 12M concentration. | In its pure state and at room temperature, it is a corrosive liquid with a strongly irritating smell. | It does not oxidize the metallic Zn since the chloride anion (in oxidation state -1) can no longer be reduced any further. | Chemistry | In an aqueous solution, it is a strong acid, although not as strong as hydrofluoric acid. | 22 | 2 | c13fd16f-0c8b-4c3e-8481-007744b1526d | 2022 |
What is the structure of quartz made of? | Tetrahedrons [SiO4] sharing edges. | Tetrahedrons [SiO4] sharing vertices. | Octahedrons [SiO6] sharing edges. | Chemistry | Octahedrons [SiO6] sharing vertices. | 23 | 1 | fc4d09be-d74a-49e1-90d9-37bb95dee31f | 2022 |
Indicate the main product of the combustion of metallic potassium with excess oxygen: | Potassium peroxide. | Potassium oxide. | Potassium ozonide. | Chemistry | Potassium superoxide. | 24 | 3 | 45635944-2397-48d8-afed-1e2fb715a19c | 2022 |
Which of the following compounds undergoes hydrolysis in water?: | MoF3. | TiCl4. | MnF2. | Chemistry | MoCl3. | 25 | 1 | 9b04cadb-454e-43b1-8de7-0d1e52eb01b7 | 2022 |
Indicate which of the following statements is false, according to Fajans' rules: | A cation is more polarizing if it is small and has a high positive charge. | The deformation of the spherical shape of an ideal anion is known as polarization. | The anions that do not have a noble gas configuration are not polarizable. | Chemistry | An anion is more easily polarized if it is large and has a large negative charge. | 26 | 4 | 58b1bab6-1ab8-4039-948d-37ffb53db46a | 2022 |
What is the name of the phenomenon in which a force acts on a moving electron or hole due to the action of a magnetic field perpendicular to the direction of movement? | Thompson Effect. | Joule Effect. | Einstein Effect. | Chemistry | Hall Effect. | 27 | 3 | fbdaa37a-f217-4216-9858-d0ce3d61119d | 2022 |
What are the methyl transfer reactions of cobalamins based on? | In the high electrophilicity of square planar Co (I). | In the high nucleophilicity of square planar Co (I). | In the low electrophilicity of tetrahedral Co (II). | Chemistry | On the low nucleophilicity of tetrahedral Co (II). | 28 | 1 | 9df47702-92a3-4525-90de-c2f2ebf880a0 | 2022 |
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