Chemistry Old Exam Questions 2022 F+-1.pdf

Chemistry MCQs ֎ 1. Which of the following is a conjugated acid-base pair? NH3 and NH4+ NH3 and NHy 2. Which one of the following is NOT a conjugate acid-base pair? HNO3 and HNO2 HNO and HNOz...

Chemistry MCQs ֎ 1. Which of the following is a conjugated acid-base pair? NH3 and NH4+ NH3 and NHy 2. Which one of the following is NOT a conjugate acid-base pair? HNO3 and HNO2 HNO and HNOz > 3. If a buffer solution of acetic acetate ion (pH= 4,74) had equal moles of HCl and NaOH added to it what would be the pH of the solution? pH=4.74 4. Which of the following is NOT a characteristic of an effective buffer? The pH is always close to 7 5. Which of the following is/are amphoteric? H 2O 6. What are the products of neutralization reaction? H20 and ionic salt 7. Xanthoproteic test is used for all amino acids described below EXCEPT: Proline Proline [The xanthoproteic reaction is a method that can be used to detect a presence of protein soluble in a solution, using concentrated nitric acid.] 8. Identify the medically important derivatives of salicylic acid: X Aspirin 9. Proteins are biopolymers of amino acids in which the monomers are linked in a linear fashion with which type of bond? Amide [The amide group is called a peptide bond when it is part of the main chain of a protein, and an isopeptide bond when it occurs in a side chain, such as in the amino acids asparagine and glutamine.] 10. What is the number of enantiomers [also called optical isomer, antipode, or optical antipode] of the following monosaccharide? 4 11. Which property is shared by amylopectin and cellulose? Both are completely composed of D-glucose 1  Chemistry MCQs ֎ 12. Which statement about metamizole is NOT correct? weak base Its structure differs from antipyrine on the position of C5-atom - (NH4Cl) / (pKb = 4.79): Henderson Hasselbach : & 13. Calculate the pH of a solution that is 0.30M in ammonia (NH3) and 0.20M in ammonia chloride 9.43 1414 79-log(38. 14. Calculate the pH of a 0.2M HCl solution: 0.7 > log (0 2) O7 - - , , 15. Which characteristic is shared by both adenine and cytosine? both are heterocyclic [Homocyclic (Heterocyclic) compounds are cyclic compounds having atoms of the same (different) element as ring members (including carbon atoms).] 16. Which characteristic is shared by purines and pyrimidines? Both can form multiple non-covalent hydrogen bonds 17. What is the pH of a buffer solution where (HA) = (A-)? pH= pKa. The species that is being reduced will have… A more negative oxidation state after the reduction has occurred 19. Soaps are… Water-soluble sodium or potassium salts of long-chain (fatty) acids X 20. Which of the following is a characteristic of the both triacylglycerols and glycerophospholipids? Both contain fatty acids and saponifiable [Triacylglycerols are formed by linking fatty acids with an ester linkage to three alcohol groups in glycerol. Triacylglycerols are the form in which fat energy is stored in adipose tissue.] 21. What is the assumption that the Henderson-Hasselbalch equation makes? X All of the above [The Henderson-Hasselbalch equation formalizes this concept, where A− is the concentration of base or hydroxide ions (OH−), and HA is the concentration of acid, or H+ ions.] 22. Phenol is less acidic than… Nitrophenol 23. Triglycerides are named because of the features they have in common. What is/are the functional groups they have in common? Glycerol and three fatty acids 24. Which component is found in both Guanosine and Uridine? Both contain three hydroxyl groups 2  Chemistry MCQs ֎ 25. Three acids found in foods are lactic acid (in milk products), oxalic acid and magic acid (in apples). The pKa values are LA= 3,88, OA=1,23 and MA=3,40. Which list has these acids in order of decreasing acid strength? OA>MA>LA [The smaller the pKa-value, the stronger the acid.] 26. Identify the two sets of conjugate acid-base pairs in the following acid-base reaction: HBr (aq) + H2O(l) → Br- (aq) + H30+ (aq) HBr/Br- and H2O/H3O+ 27. Which statement is TRUE for the final reaction step in the Ostwald process (the process is used for the commercial production of nitric acid) expressed with the following chemical equation: NO2 (g) + H2O (l) → HNO3 (aq) + NO (g) The reaction is not balanced 28. Ammonia (NH3) acts as a weak base in aqueous solution. What is the acid that reacts with this base when ammonia is dissolved? None, there are no acids in pure water 29. What would you react with an aldehyde to form a carboxylic acid but NOT react with an alcohol? Tollens’ reagent [Tollens’ reagent is a chemical reagent used to distinguish between aldehydes and ketones along with some alpha-hydroxy ketones which can tautomerize into aldehydes. The reagent consists of a solution of silver nitrate, ammonia and some sodium hydroxide (to maintain a basic pH of the reagent solution).] 30. Which of the following is NOT a component of phospholipid? Glucose 31. Identify the acid which is NOT a metabolite in citric acid cycle: Maleic 32. Which of the following has powerful antiseptic action? X Salicylic acid 33. The isoelectric point of an amino acid is defined as… The pH where the molecule carries NO net electric charge 34. Identify the amino acids containing positively charged, basic R groups: Lysine, Arginine, Histidine 35. When comparing amylose to glycogen… Only glycogen contains 1,6 glycosidic bonds 36. Which property differs between amylose and cellulose? The orientation of the glycosidic bonds 3  Chemistry MCQs ֎ 37. The sugar molecule in a Nucleotide is a… Pentose X 38. When protein is present, biuret turns… Violet 39. Which chemical did you mix to test for proteins – biuret test? Sodium hydride and copper sulphate 40. What is the name of the chemical from the reaction between methanol acid and ethanol? Ethyl methanoate 41. Which of the following is TRUE about esters? They are more volatile than carboxylic acids of similar molecular weight [Alcohols can combine with many kinds of acids to form esters. When no type of acid is specified, the word ester is assumed to mean a carboxylic ester, the ester of an alcohol and a carboxylic acid. The reaction, called Fischer esterification, is characterized by the combining of an alcohol and an acid (with acid catalysis) to yield an ester plus water.] 42. What observations would you expect to see in a positive Fehling’s test for an aldehyde? X Blue solution to Brick-red solid 43. The key characteristics of redox reduction is the… Passing of one or more electrons from one species to another 45. Identify the purine base of the nucleic acids in the following… Adenine 46. Which of the following is a conjugate acid-base pair? HI and I- 47. Which one of the following is NOT a conjugate acid-base pair? H3O+ and OH- 48. Which of the following can be mixed together in water to produce a buffer solution? H3PO4 and NaH2PO4 49. What does the buffer capacity (effectiveness) depend on? All answers are correct [The capacity of a buffer to neutralize added acid or base depends on the concentrations of HA and A⁻ in solution. For a given ratio of [HA] to [A⁻], the greater the concentrations, the higher the overall buffer capacity. When [HA] is greater than [A⁻], the capacity is higher for added base than acid.] 4 Chemistry MCQs ֎ 50. How many times more acidic is a solution with a pH of 3 compared to absolution with a pH of 6? 1000 [The pH scale is logarithmic, meaning every whole number change on the scale reflects a ten-fold change in acidity. Since a pH of 3 is three numbers higher than a pH of 6, we can find the change in acidity by taking 10 to the third power. 10∗10∗10=1000] 51. What reaction occurs as a hydrochloric acid solution is added to a solution containing equal concentrations of acetic acid and sodium acetate? CH3COO- + H+ → CH3COOH 52. What is the assumption that Henderson-Hasselbalch equation makes? All of the above 53. Identify all the correct statements about an acid-base buffer solution? All would give buffer solutions (II, III, IV and V) 54. Which of the following statements concerning the oxidation of aldehydes and ketones is correct? Aldehydes readily undergoes oxidation and ketones are resistant to mild oxidation 55. Which of the following molecules is typical fatty acids? A molecule that has one cis double bond in a linear carbon chain. [Generally, a fatty acid consists of a straight chain of an even number of carbon atoms, with hydrogen atoms along the length of the chain and at one end of the chain and a carboxyl group (―COOH) at the other end. It is that carboxyl group that makes it an acid (carboxylic acid).] 56. Which of the following carbolic acids or carboxylic acid derivatives is the most reactive to a nucleophilic attack at the carbonyl carbon? CH3CH2COOH [A nucleophilic attack often occurs when an electron-rich species (the nucleophile) "attacks" an electron- deficient species (the electrophile, usually a carbocation), forming a new bond between the nucleophile and the carbocation.] 57. Which statements is TRUE about phenols? Delocalization of negative charge in phenoxide ion makes phenoxide ion more stable than phenol favoring the ionization of phenol 58. What is the main product of the reaction when butanoic acidic reacted with ethanol? An ester 59. Which of the following reaction is NOT shown by ketones? Reaction with Fehling‘s solution 5 Chemistry MCQs ֎ 60. Hydrolysis of fat by alkali is called... Saponification [Saponification is the formation of a metallic salt of a fatty acid; such a salt is called a soap. The reaction involves treatment of free fatty acids and/or glycerides with a base and may be considered a special case of hydrolysis when a glyceride is reacted with a base.] 61. Which property does this lipid share with a typical triacylglycerol? Both are saponifiable 62. What type of reaction used to break down methyl pentanoate into methanol and pentatonic acid? Hydrolysis [Hydrolysis is a chemical reaction of the interaction of chemicals with water, leading to the decomposition of both the substance and water. Reactions of hydrolysis are possible with salts, carbohydrates, proteins, fats, etc.] 63. Which of the following acids has at least two chiral centers? Tartaric acid 64. Which property is found in nucleosides and nucleotides? Both contain an anomeric carbon atom that is part of α β -N-glycosidic bond 65. Tuberculosis is a disease caused by bacteria called Mycobacterium tuberculosis. It has been treated with antibiotic... Para-amino salicylic acid 66. How many asymmetrical carbon atoms are presented in the molecule of citric acid? None 67. Which product could be formed form the breakdown of the polysaccharides amylopectin and cellulose? Amylopectin could be broken down into maltose 68. All of the following are nonvolatile, aliphatic amino acids EXCEPT... Lysine 69. Aspirin is converted into salicylic acid in your body by which of the following reactions? Hydrolysis 6 Chemistry MCQs ֎ 70. Which of the following acids is dicarboxylic? Oxalic acid [A dicarboxylic acid is an organic compound containing two carboxyl functional groups (−COOH). Oxalic acid is the most important dicarboxylic acid.] 71. The acid present in sour milk is... Lactic acid 72. What is a maltose? A disaccharide composed of glucose 73. The disaccharide _____ consists of α-glucose and β-fructose. Sucrose 74. Hydrolysis of cellobiose yields: β-glucose and α/β-glucose 75. Polysaccharides contain 1,4-glycosidic bonds [1,4-glycosidic bonds can be found in both amylase and amylopectin in starch. These linkages create branching in the polysaccharide. There are many glycosidic linkages in polysaccharides due to the large number of hydroxyl groups present.] 76. Which property is shared by amylopectin and cellulose [polysaccharides]? Both are composed entirely of D-glucose 77. Which characteristic distinguishes amylopectin and glycogen? They have different degrees of branching 78. Amylose and cellulose…. Both are homopolysaccharides 79. When comparing amylose to glycogen: Only glycogen contains 1,6 glycosidic bonds 80. What is the monosaccharide when amylose is being hydrolyzed? Glucose 81. Identify the amino acids containing non-polar, aliphatic R groups: Glycine, Alanine, Leucine 82. The two amino acids having R groups with a negative net charge at pH 7.0 are: Aspartate and glutamate 83. If pK1 = 2.34 and pK2 = 9.60, then the isoelectric point (pI) is: 5,97 0. 5 (2 34 + 9 60) = 5 97 -. ,. 7 Chemistry MCQs ֎ 84. According to biochemical classification of amino acids valine is: with non-polar side chain 85. Serine is: An amino acid with polar side chain [Some amino acids have polar side chains that are soluble in water; examples include serine, threonine, and asparagine. Other amino acids avoid water and are called hydrophobic, such as isoleucine, phenylalanine, and valine.] 86. Which among the following is a non-essential amino acid? Serine [Nonessential amino acids are synthesized by most of the cells, including hematopoietic lineages. Nonessential amino acids are mainly synthesized from glucose (alanine, arginine [from the urea cycle in hepatic cells], asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, and serine), except for tyrosine, which is synthesized from phenylalanine. The rest of the nine amino acids are essential and the body needs to obtain these from the diet.] 87. Which among the following is an essential amino acid? Phenylalanine 88. The number of chiral centers in leucine (Leu) [Isoleucine (Ile)] is: 1 [Group I amino acids are glycine, alanine, valine, leucine, isoleucine, proline, phenylalanine, methionine, and tryptophan. The R groups of these amino acids have either aliphatic or aromatic groups. This makes them hydrophobic (“water fearing”) Isoleucine is an isomer of leucine, and it contains two chiral carbon atoms.] 89. Which of the following will NOT be reactive towards Seliwanoff reagent? Maltose [Seliwanoff's test is a chemical test which distinguishes between aldose and ketose sugars. If the sugar contains a ketone group, it is a ketose. Maltose is an aldose sugar and only ketoses give a positive Seliwanoof’s test. Sucrose, Inulin and fructose contain a ketose, and maltose does not. Only Therefore, sucrose, Inulin and fructose will give a positive Seliwanoof’s test, but maltose will not.] 90. Which of the following will be positive towards iodine test? Starch [The iodine–starch test is a chemical reaction that is used to test for the presence of starch or for iodine. The combination of starch and iodine is intensely blue-black.] 91. If _____ are treated with strong acid such as sulfuric acid at high temperatures, they are first hydrolyzed to the component _____. Polysaccharides, monosaccharide 8 Chemistry MCQs ֎ 92. If one treats _____ with sulfuric acid, glucose is obtained in high yield with little secondary decomposition. Starch (Cellulose) [Starch, a white, granular, organic chemical that is produced by all green plants. Starch is a soft, white, tasteless powder that is insoluble in cold water, alcohol, or other solvents. The basic chemical formula of the starch molecule is (C6H10O5)n. Starch is a polysaccharide comprising glucose monomers joined in α 1,4 linkages. The simplest form of starch is the linear polymer amylose; amylopectin is the branched form.] 93. The red precipitate formed when glucose is heated with Benedicts reagent is: Cupric oxide [Benedicts reagent is a chemical reagent and complex mixture of sodium carbonate, sodium citrate, and copper (II) sulfate pentahydrate. It is often used in place of Fehling's solution to detect the presence of reducing sugars.] 94. The following sugar exhibits inversion of optical rotation on heating with dilute acid: Sucrose 95. The reagent used for distinguishing a reducing monosaccharide from a reducing disaccharide is: Barfoed’s reagent 96. What is the definition of a dipeptide? Two amino acids joint together 97. Proteins are biopolymers of amino acids in which the monomers are linked in a linear fashion with which type of bond? Amide bonds [Proteins are polymers in which the 20 natural amino acids are linked by amide bonds.] 98. A tripeptide has: 3 amino acids and 2 peptide bonds [A tripeptide is a peptide derived from three amino acids joined by two or sometimes three peptide bonds. As for proteins, the function of peptides is determined by the constituent amino acids and their sequence. The simplest tripeptide is glycylglycylglycine.] 99. Which chemicals do you mix to test for proteins (biuret test)? Sodium Hydroxide and Copper Sulphate 100. Xanthoproteic test is specific for: Tyrosine [Xanthoproteic test is used to detect amino acids containing an aromatic nucleus (tyrosine, tryptophan and phenylalanine) in a protein solution which gives yellow color nitro derivatives on heating with conc. HNO3. The aromatic benzene ring undergoes nitration to give yellow colored product.] 101. Xanthoproteic test is used for all amino acids described below EXCEPT: Proline (Glycine, Alanine) 9 Chemistry MCQs ֎ 102. Which test will you use for the presence of proteins? Biurets test 103. The two amino acids having R groups with a negative net charge at pH = 7.0 are: Aspartate and Glutamate 104. The three amino acids having R groups with a positive net charge at pH = 7.0 are: Lysine, Arginine, Histidine 105. Which of the following is an essential amino acid? Phenylalanine 106. What test will you use to distinguish valine from glutathione? Biuret test. The disaccharide _______ consists of α-glucose and fructose. Sucrose 108. Amylopectin and cellulose: contain 1,4-glycosidic bonds [Cellulose consists of linear chains of mutually interlinked—from a few hundred to over ten thousand— glucose units, which are, as with starch, interconnected with a glycosidic bond. Although starch and cellulose have the same monomer unit, their polymeric chains differ in the orientation of glucose units.] 109. The following sugar exhibits inversion of optical rotation on heating with dilute acid? Sucrose 110. Reduction of glucose yields: Sorbitol [The aldehyde reduction product of glucose is the molecule sorbitol. Glucose is an aldehyde; fructose is a ketone.] 111. Which sugars are present in Sucrose? Fructose and glucose 112. Which of the following is NOT a disaccharide? Galactose 113. The alkaline hydrolysis of oils and fats is called: Saponification 114. What three amino acids make up glutathione? Glutamic acid, cysteine and glycine [Glutathione is found in the diet and is also synthesized in the body. Heavy metals and fat-soluble toxins are the main binding substrates for glutathione, making them water-soluble for kidney excretion.] 10 Chemistry MCQs ֎ 115. Which of the monosaccharides should react to produce lactose? Galactose and glucose 116. Pi and Sigma bonds carbonyl group have: one strong sigma and one weak pi 117. Which is a general property of both nucleosides and nucleotides? Both contain a pentose in the form of a furanose [compare with 64.] 118. Which characteristic is found in both purines and pyrimidines? They both can form stable N-glycosidic bonds with β D-ribofuranose 119. Which property is shared by both GDP and A? Both contain the same furanose 120. Which component is found in both adenosine and deoxycytidine? Both contain a ’-OH group 121. Which structural feature is shared by both uracil and thymine? Both contain two keto groups *122. Which property is shared by both CTP and dTDP? Both contain a planar six-membered ring *123. One of the following has reducing properties: Glucuronic acid [A form of a type of sugar called glucose that helps remove harmful substances from the body. Glucuronic acid and the harmful substance combine in the liver and then are passed in the urine.] *124. Which characteristic is different when comparing the open-chain forms of D-sorbose and D- ribose? the number of primary alcohol groups *125. Which characteristic is shared by the ring forms of D-sorbose and D-galactose? Both can undergo mutarotation *126. Which describes the relationship between D-sorbose and D-fructose? They are diastereomers but not epimers *127. The enantiomer of D-sorbose: is an L-sugar that has opposite configuration around three carbons. *128. Which reagent will oxidize D-sorbose? Alkaline cupric ion *129. When 3.0 moles of D-sorbose are completely oxidized by periodate: six moles of formaldehyde are produced *These questions are from a third source and are most likely not on the MCQ test. 11 Chemistry MCQs ֎ *130. When comparing D-sorbose with D-glucose: They have the same chemical formula *131. When comparing D-talose to D-fructose: D-gulose has the same number of carbon atoms as D-fructose *132. When comparing D-talose to D-ribose: D-gulose has more diastereomers than D-ribose *133. What is the relationship between D-talose and D-galactose? They are C-2 epimers *134. The open-chain structure of L-talose: has one OH group pointing left *135. Which of the following is a reaction of D-talose? It will be converted into an aldaric acid by nitric acid *136. When 2.0 moles of D-talose are completely oxidized by periodate: 2 moles of HCHO are produced *137. The complete name of this structure is: β-D-gulopyranose *138. What characteristic is shared by D-gulose and D-glucose? They both have two anomeric forms *139. When D-gulose is written in the open-chain form: three OH groups are on the right and one OH group is on the left *140. When D-gulose forms a ring structure: the ring is unstable at neutral pH *141. The anomeric forms of D-gulose: have different numbers of axial substituents *142. When D-gulose is treated with Benedict’s reagent: it will oxidize into an aldonic acid *These questions are from a third source and are most likely not on the MCQ test. 12 Chemistry MCQs ֎ *143. When comparing D-gulose and a D-ketohexose both can interconvert between α and β forms *144. If D-gulose is converted into a monosaccharide derivative: it forms a deoxy sugar that could mutarotate *145. The name of this structure is: α-D-arabinofuranose *146. What is the relationship between D-arabinose and D-ribose? They are epimers that both give a positive reaction with Benedict’s reagent *147. When D-arabinose is written in its open-chain form: the hydroxyls on C-3 and C-4 point right while the hydroxyl on C-2 points left 148. Specify if the following sugars are reducing or non-reducing: Lactose – reducing sugar Sucrose – non-reducing sugar Maltose – reducing sugar Fructose – reducing sugar Glucose – reducing sugar Galactose – reducing sugar Maltose – reducing sugar Mannose – reducing sugar [The main difference between reducing and nonreducing sugar is that reducing sugars have free aldehyde or ketone groups whereas nonreducing sugars do not have free aldehyde or ketone groups.] 149. Consider the following structure: CH3 ― CH2 ― OH Name the compound: Ethanol Classify is as primary, secondary or tertiary: primary Upon oxidation it yields: acetaldehyde [and further oxidized to acetic acid, depending on the reagents and conditions.] 150. Consider the following structure: Name the compound: 2-Propanol (IUPAC-Name Propan-2-ol) Classify as primary, secondary or tertiary: secondary Upon oxidation it yields: Propanone (Ketone) *These questions are from a third source and are most likely not on the MCQ test. 13 Chemistry MCQs ֎ 151. Which of the following reaction is NOT shown by ketones? Reaction with Fehling’s solution 152. Which of the following equations correctly interrelates [ H+ ] and [ OH- ]? [ H+] * [ OH- ] = Kw = 1.0 * 10 -14 153. Identify the reducing sugars among the examples: 1 2 3 5 6 1 1, 2, 3, 5 and 6 154. Which characteristic is most likely shared by a cell membrane and a lipoprotein particle? Both contain hydroxyl groups on the surface 155. At which pH all amino acids will have a – 1 charge? 10.6 156. Which characteristic is shared by this lipid and an eicosanoid? This lipid and a leukotriene are both polyunsaturated molecules 157. Which property can be shared by this lipid and a terpene? Both can be very hydrophobic molecules 158. Which property is shared by integral membrane proteins and peripheral membrane proteins? Both can contain regions of α-helices and β-pleated sheets 159. Which type of membrane lipid contains an acidic oligosaccharide? Ganglioside 160. Which is a property of integral membrane proteins? All integral membrane proteins contain hydrophilic regions 14 Chemistry MCQs ֎ 161. At which pH will half the amino acid molecules have a +1 charge? 5.5 162. Which one of the following gives a ketone upon oxidation? Secondary alcohol. Catalytic dehydrogenation of primary alcohol gives a… Aldehyde 164. What are the missing groups (A and B) in citric acid chemical formula? → (A) – COOH and (B) – OH 165. When reacted with a strong reducing agent, aldehydes turn into: Primary alcohols 166. Which of the following molecules is a typical fatty acid? A molecule that has one cis double bond in a linear carbon chain 167. In which equation H2O acts only as Brønsted-Lowry acid: H2O + NH3 → NH4OH [A Brønsted-Lowry acid is any species that is capable of donating a proton H +. A Brønsted-Lowry base is any species that is capable of accepting a proton, which requires a lone pair of electrons to bond to the H+. Water is amphoteric, which means it can act as both a Brønsted-Lowry acid and a Brønsted-Lowry base.] 168. Ethanol can be converted to ethanal by process of: Oxidation 169. What is/are the products of a reaction between propanoic acid and sodium hydroxide? Sodium propanoate and water 170. The products of the reaction of a carboxylic acid and an alcohol would be: Ester and water 171. Which of the following acids does NOT exhibit optical isomerism? Malic acid 172. Which condensed formula might an ester have? CH3COOCH3 15 Chemistry MCQs ֎ 173. Which monosaccharides react to produce lactose? β-D-Galactose and α/β-D-Glucose 174. When the alcohol group is oxidized it yields: A carbonyl group 175. What is the common name of the cis isomer of but-2-enedioic acid? Maleic acid 176. In what product results 4-hydroxy pentanoic acid upon heating? Lactone 177. Which statement is TRUE about phenols? In phenol, the – OH group is attached to sp2 hybridized carbon which is more electronegative, hence the – OH bond become more polar. 178. Phenol is less soluble in water compared to ethanol. It is due to: Non-polar hydrocarbon part of it 179. In the compound below, which of the following substituents replacing X would result in acylhalide? Cl *180. What is the proper designation for the unsaturated fatty acids in this lipid? : (Δ6,9) 181. Which characteristic is shared by a cell membrane and a chylomicron? Both contain specific proteins 182. The boiling point of alcohols is much higher than ethers and other classes of compounds with similar molecular masses. Give a reason. Due to intermolecular hydrogen bonding in alcohols 183. Which of the following make the best buffer? A solution of ammonia and ammonium chloride NH3 and NH4Cl 184. Identify the medically important derivatives of salicylic acid: Ai spiri 185. Name the following reaction and predict the product X obtained: R’COOH + R’OH → X + H2O (→ H2SO4) The name of the reaction is esterification and product X is an ester with the formula R’COOR 16 Chemistry MCQs ֎ 186. Which is a characteristic of sphingolipids? They all contain ceramide joined to a polar group 187. Which is a characteristic of the component in cell membranes? A lipid molecule in a membrane interacts with other membrane molecules through non-covalent forces *188. Which structural feature is found in the single-stranded DNA molecule? Each ’, ’-phosphodiester bond will contain one phosphate group linking two deoxyribose sugars *189. Which is a difference between integral membrane proteins and peripheral membrane proteins? Integral membrane proteins bind to the membrane using hydrophobic forces while peripheral membrane proteins bind to the membrane using hydrophilic forces *. Which characteristic will be shared when comparing the single ’-(GA)20- ’ strand to another single-stranded DNA molecule with the sequence ’-(AT)20- ’? Both will have the same overall charge 191. Which of the following is a characteristic of both waxes and terpenes? Both can contain oxygen 192. Which are the products of the following reaction? H - + S02 + H( RCOCl, SO2 and HCl 193. Oxidation of which of the following alcohols will produce a ketone? 194. The structure below is? Protoporphyrin 17 Chemistry MCQs ֎ 195. Which of the following structures is a triglyceride? *. Which of the following structures is a : (Δ4,9) fatty acid? CH3(CH2)9CH = CH(CH2)3CH = CH(CH2)2COOH 197. Which is a characteristic of all the fatty acid components in this lipid? They all contain an unbranched carbon chain 198. Which characteristic does this lipid share with a wax? Both contain one or more ester bonds 199. Which membrane lipid contains an amide bond? Sphingomyelin 200. Which is a property of lipids in cell membranes? Some types of lipids are found preferentially in the outer membrane layer 201. Which type of membrane lipid could contain serine? a glycerophospholipid 202. Which component is found in all sphingolipids? an amino alcohol 203. Which will be a characteristic of a steroid that is part of a cell membrane? It will contain a hydroxyl group 204. Which of the following carboxylic acids or carboxylic acid derivatives is the most reactive to nucleophilic attack at the carbonyl carbon? CH3CH2COOH 205. Which characteristic does the double-stranded molecule have when it forms a B – DNA structure? Every base-pair will contain one purine and one pyrimidine 206. What is maltose? A disaccharide composed of glucose *. Which type of product is formed when Cold dilute alkaline solution of Bayer’s reagent reacts with alkene? Syn-glyol 18 Chemistry MCQs ֎ 208. At which pH will all the amino acids molecules be in their fully protonated form? 6.1 208 (1) At which pH will all amino acids molecules be in their zwitterion form? 6.1 208 (2) At which pH will all amino acids molecules have a + 1 charge? 5.5 208 (3) At which pH all the amino acids molecules have a – 1 charge? 8.2 209. What test will you use to distinguish a value from glutathione? Biuret test [Glutathione is made up of three amino acids—cysteine, glutamic acid, and glycine. Glutathione is found in the diet and is also synthesized in the body. Heavy metals and fat-soluble toxins are the main binding substrates for glutathione, making them water-soluble for kidney excretion.] 210. If pK1 = 2.34 and pK2 = 9.60, then the isoelectric point (pl) is: 5.97 211. Which of the following compounds exhibits optical isomerism? A [D-(-) tartaric acid] 19 Chemistry MCQs ֎ 212. Name the following compounds: [A] 2-Methylpropanoic acid; [B] D-(-) Tartaric acid; [C] Ethyl ethanoate 213. Which of the following compounds: ethers (I); esters (II); acid anhydrides (III); nitrites (IV); amides (V) form in the reactions with water, carboxylic acids? (II), (III), (IV) & (V) all except esters 214. When an alcohol molecule adds across a carbon-oxygen double bond of an aldehyde or ketone, the… OR portion from the alcohol bonds to the carbonyl C-atom 215. Which of the following statements is NOT true about the following reaction? None of the species is undergoing oxidation or reduction 216. Which of the structure below corresponds to serotonin? 20 Chemistry MCQs ֎ 217. What is the major organic compound obtained from the following reaction? 218. What is the major organic compound obtained from the following reaction? 219. Among the following salicylic acid derivatives, identify the one that does NOT contain an ester group: Para-amino salicylic acid (PASA) or Sodium Salicylate 220. Examine the membrane lipid pictured below. Which of the statements below are TRUE about it? I. This lipid is sphingolipid II. This lipid is classified as glycerophospholipid III. The fatty acids chain in this lipid are saturated IV. Phosphoric acid forms a diester with glycerol and the amino alcohol (II), (III) & (IV) 221. Which two chemicals would be used to make ethyl propanoate? (5) and (3). What are the products of the reaction between butanone and Tollen’s reagent? no reaction 21 Chemistry MCQs ֎ 223. Which reaction(s) show acidic nature of phenol? (I) & (III) 224. When [H+] = 1.0*10-7 M in water at 25°C, then… [OH-] = 1.0*10-7 M 225. Which statement is NOT correct? Pure water at ° C has… All are correct 226. Identify the equation for the dissociation of the weak acid hydrofluoric acid (HF) in water: HF (aq) + H2O (l) → F- (aq) + H3O+ (aq) 227. What is the formula for determining [OH-] in a solution when given the concentration of hydronium ions? [OH-] = Kw/[H3O+] 22 Chemistry MCQs ֎ 228. Which of the following compound would be most resistant to oxidation with a mild oxidizing agent? C 229. In which equation is esterification present? A. Vitamin B is the name given to three related derivatives. They are… (I), (II) & (IV) 23 Chemistry MCQs ֎ 231. Which of the following substances is used as catalyst in esterification reactions? Sulfuric acid 232. Number of chiral centers in glycine (Gly) is… 0 233. All of the following are polar amino acids EXCEPT: Alanine 234. What test will you use to distinguish valune from glutation? Biuret test 235. Type of bonds between COOH terminal of one amino acid and NH2 terminal of another amino acid is: All answers are correct. The carbon atom of the carbonyl group is… sp2 hybridized 237. The oxidizing agent in the Tollen’s test for the presence of an aldehyde is… Ag+ 238. In the compound below, which of the following substituents replacing X would result in an ester? OCH3 239. Which of the following properties of the carbonyl group allows aldehydes and ketones to undergo nucleophilic addition reactions? Polarity of the carbon – oxygen bond 240. The carbonyl-group carbon of aldehydes and ketones is susceptible to nucleophilic attack because: It has a partial positive charge (δ+). You are performing a Fehling’s test with propenal. What are the products of this reaction? Propanoic acid, Cu2O, H2O. Propanone is very soluble in water because… It can form intermolecular hydrogen bond with water molecule. The peptide bond in proteins is… Planar and fixed in a trans conformation 244. Buffering capacity is expressed mathematically as follows: 24 Chemistry MCQs ֎ 245. A solution that contains a weak acid and its conjugate base in roughly equal concentrations is… a buffer Essay Questions: 246. How do buffers work? Buffers work by neutralizing any added acid (H+ ions) or base (OH- ions) to maintain the moderate pH, making them a weaker acid or base. Let’s take an example of a buffer made up of the weak base ammonia, NH3 and its conjugate acid, NH4+. When HCl (strong acid) is added to this buffer system, the extra H+ ions added to the system are consumed by the NH3 to form NH4+. Now, because all the extra H+ ions are locked up and have formed a weaker acid, NH4+, thus the pH of the system does not change significantly. Similarly, when NaOH (strong base) is added to this buffer system, the ammonium ion donates a proton to the base to become ammonia and water thus neutralizing the base without any significant pH change. 247. Give a definition for power of hydrogen (pH). List the methods of determination: pH, quantitative measure of the acidity or basicity of aqueous or other liquid solutions. It translates the values of the concentration of the hydrogen ion (H+) —which ordinarily ranges between about 1 and − gram-equivalents per liter—into numbers between 0 and 14. Litmus Paper – Acid or Base Full and short – range pH paper – color compared to pH scale pH meter – measures the hydrogen ion activity 248. What is the concept of autoionization of water? Water can undergo autoionization to form H3O+ and OH ions. The equilibrium constant for the autoionization of water, Kw, 10-14 at 25∘ C. In a neutral solution, [H3O+] = [OH-] In an acidic solution, [H3O+] > [OH-] In a basic solution, [OH-] > [H3O+] For aqueous solutions at 25°C, the following relationships are always true: Kw = [H3O+][OH-]= 10-14 pH + pOH = 14 The contribution of the autoionization of water to [H3O+ and OH-] becomes significant for extremely dilute acid and base solutions. Water is one of the most common solvents for acid-base reactions. Water is amphoteric, capable of acting as either a Brønsted-Lowry acid or base. 25 Chemistry MCQs ֎ 249. Draw the structural formula of lactose. What type of linkage is present in the disaccharide? β – 1,4 – Glycosidic bond 250. Give a definition and an example of a buffer solution. The Henderson-Hasselbalch equation for an alkaline buffer system: Buffer solutions are solutions which resist change in pH upon addition of small amounts of acid or base. Usually consist of either a weak acid with its conjugate base or a weak base with its conjugate acid. An example is, Borate (2). [𝐴−] [𝑐𝑜𝑛𝑗𝑢𝑔𝑎𝑡𝑒 𝑏𝑎𝑠𝑒] Equation: (1) pH = pKa + log ( [𝐻𝐴] ) (for weak acid) [𝑤𝑒𝑎𝑘 𝑎𝑐𝑖𝑑] [𝐵] [𝑐𝑜𝑛𝑗𝑢𝑔𝑎𝑡𝑒 𝑏𝑎𝑠𝑒] (2) pOH = pKb + log ( [𝐵𝐻+] ) (for weak base) [𝑤𝑒𝑎𝑘 𝑏𝑎𝑠𝑒] 251. Bronsted-Lowery concept for acids and bases. Give an example of Bronsted-Lowery acid and base: According to the Brønsted-Lowry scheme a substance can function as an acid only in the presence of a base; similarly, a substance can function as a base only in the presence of an acid. Furthermore, when an acidic substance loses a proton, it forms a base, called the conjugate base of an acid, and when a basic substance gains a proton, it forms an acid called the conjugate acid of a base. Thus, the reaction between an acidic substance, such as hydrochloric acid, and a basic substance, such as ammonia, may be represented by the equation: 252. What is titration and how is the process carried out? Titration, process of chemical analysis in which the quantity of some constituent of a sample is determined by adding to the measured sample an exactly known quantity of another substance with which the desired constituent reacts in a definite, known proportion. The process is usually carried out by gradually adding a standard solution (i.e., a solution of known concentration) of titrating reagent, or titrant, from a burette, essentially a long, graduated measuring tube with a stopcock and a delivery tube at its lower end. The addition is stopped when the equivalence point is reached. At the equivalence point of a titration, an exactly equivalent amount of titrant has been added to the sample. The experimental point at which the completion of the reaction is marked by some signal is called the end point. This signal can be the color change of an indicator or a change in some electrical 26 Chemistry MCQs ֎ property that is measured during the titration. The difference between the end point and the equivalence point is the titration error, which is kept as small as possible by the proper choice of an end- point signal and a method for detecting it. 27