Chemistry Topic 10 (Exam-ish Style Questions)

different

Are the empirical and molecular formulas of ethane the same or different? Answer with same or different.

i) CH3OCH2CH3; CH3CHOHCH3 ii) CH3CHOHCH3 has a higher boiling point due to hydrogen bonding; CH3OCH2CH3 has a lower boiling point due to van der Waals forces; hydrogen bonds in CH3CHOHCH3 are stronger

Propan-1-ol has two structural isomers. i) Deduce the structural formula of each isomer ii) Identify the isomer from part above which has the higher boiling point and explain your choice. Refer to both isomers in your explanations

a) Same functional group; successive members differ by CH2; same general formula; similar chemical formula; graduation in physical properties b) Y: 4-methylpentanal; Z: 4-methylpentanoic acid

One example of homologous series is the alcohols. a) Describe two features of a homologous series. b) Consider the following reactions. (CH2)2CH(CH(CH2)2OH (X) -> (CH2)2CH(CH2)2CHO (Y) I (CH2)2CH(CH(CH2)COOH (Z) The IUPAC name of X is 4-methylpentan-1-ol. State the IUPAC names of Y and Z

1. Find the longest continuous chain of carbon atoms to find the stem of the name: 1C (meth-), 2C (eth-), 3C (prop-), 4C (but-), 5C (pent-), 6C (hex-). 2. Check for single, double or triple bonds in the chain: only single bonds (-an-), a double bond (-en-), a triple bond (-yn-). 3. Check for functional groups and add their prefix or suffix to the name. 4. Add a number to indicate the position of the functional group. 5. If more than one of the same functional group is present, use di (for 2), tri (for 3) or tetra (for 4).

Outline how organic compounds are named according to the nomenclature of IUPAC.

The oxidation of a primary alcohol is a two step process that first produces an aldehyde which is further oxidised to a carboxylic acid. Propanoic acid

Propan-1-ol is heated with acidified KMnO4 using a reflux column. Outline the reaction process and give the IUPAC name of the final product

D. The movement of a pair of electrons

What do 'curly arrows' show when used to illustrate a nucleophilic substitution reaction mechanism? A. The movement of an electron. B. The heterolytic fission of a bond C. The homolytic fission of a bond D. The movement of a pair of electrons

D. propyl methanoate

What is the IUPAC name for the compound HCOOCH2CH2CH3? A. propyl ethanoate B. ethyl ethanoate C. methyl propanoate D. propyl methanoate

B. water and carbon monoxide

Which products are most likely to be formed if excess butane is burned in a limited supply of air? A. hydrogen and carbon B. water and carbon monoxide C. hydrogen and carbon dioxide D. hydrogen and carbon monoxide

C. CH3CH2.+CH3CH2.→CH3CH2CH2CH3

Which reaction could be a termination step in the reaction of ethane and chlorine in the presence of ultraviolet light? A. CH3CH2+ + Cl- → CH3CH2Cl B. CH3CH2.+ Cl → CH3CH2Cl + Cl. C. CH3CH2.+CH3CH2.→CH3CH2CH2CH3 D. CH3CH3 + Cl. → CH3CH2. + HCl

A. Bromine water

Which reagent can be used to distinguish easily between an alkene and an alkane? A. Bromine water B. Acidified potassium dichromate solution C. Chlorine in ultraviolet light D. Sodium hydroxide solution

A. sodium borohydride

Which reagent(s) can be used to convert propanone, CH3COCH3, into propan2-ol, CH3CH(OH)CH3? A. sodium borohydride B. acidified potassium dichromate solution C. sulfuric acid D. sodium hydroxide solution

D. BF3

Which species cannot act as a nucleophile? A. H2O B. CN- C. NH3 D. BF3

A. Cl.

Which species is a free radical? A. Cl. B. Cl+ C. Cl- D. Cl:

B. CH3OH. C2H5OH, C3H7OH

Which three compounds form part of a homologous series? A. C2H2, C2H4, C2H6 B. CH3OH. C2H5OH, C3H7OH C. CH3CH2CH2CH2OH, CH3CH2CH(OH)CH3, CH3CH(CH3)CH2OH D. CH3CH2CHO, CH3COCH3, CH3CH2CH2OH

They have no hydrogen atoms attached to the carbon atom holding the -OH group.

Why can't territory alcohols be oxidised?

The type of reaction is nucleophilic substitution. A nucleophile contains a lone pair of electrons and a full negative charge, like -OH. The partial charge of the carbon atom in the polarised C-Cl bond attracts nucleophiles. 2,2-dimethylpropanol

1-chloro-2,2-dimethylpropane is reacted with an aqueous solution of sodium peroxide. What is the reaction? State the IUPAC name of the product.

In complete combustion reactions oxygen is in excess, so the propane completely reacts with oxygen to produce carbon dioxide and water: C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)

1. Deduce the equation for the complete combustion of propane.

1. Structural isomers are compounds that have the same chemical formula but different structural formulae (different arrangement of atoms). 2. n-butane, 2-methylpropane

1. Define the term structural isomers. 2. Draw the structural isomers of butane (C4H10) and name each of them.

C. C3H6

A hydrocarbon, X, decolourises aqueous bromine, Br2 (aq). Which one of the following molecular formulas could be X? A. CH4 B. C6H14 C. C3H6 D. C5H12

In addition polymerization, small monomers that contain a C=C double bond link together to form a longer polymer. During this process the double bonds in the monomers are converted into single bonds in the polymer.

Addition polymers are made of a wide variety of monomers and form the basis of the plastic industry. Outline the addition polymerisation of tetrafluoroethene C2Fl4

Free radical substitution

Alkanes can react with halogens in a photochemical reaction under conditions involving UV light. What type of mechanism is involved in this reaction? (you should include the type of reactive species involved in the mechanism in your answer - the word 'reaction' is not necessary).

a) Boiling points increase (from the first member to the fifth members); increasing size of molecules; strength of intermolecular forces increase therefore more energy is required to break the intermolecular bonds b) Same functional group; successive members differ by CH2; same general formula; similar chemical formula; graduation in physical properties

Alkenes are important starting materials for a variety of products. a) State and explain the trend of the boiling points of the first five members of the alkene homologous series. b) Describe two features of a homologous series

a) i) methylpropene ii) C4H8 (g) + 6O2 (g) -> 4CO2 (g) + 4H20 (l) b) i) structural isomers ii) react with bromine water in the light; A: from yellow/brown to colourless + B: colour remains/slowly decolonized

Alkenes are widely used in the production of polymers. The compound A, shown below, is used in the manufacture of synthetic rubber. a) i) State the name, applying IUPAC, of compound A. ii) Compound A is flammable. Formulate the equation for its complete combustion. b) Compound B (cyclobutane) is related to Compound A i) State the term that is used to describe molecules that are related to each other in the same way as Compound A and Compound B. ii) Suggest a chemical test to distinguish between compound A and compound B, giving the observations you would expect for each

Nickel or Palladium or Platinum

Alkenes undergo addition reactions. Which metal catalyst is often used in the hydrogenation reactions that converts them into alkanes? State the name of the catalyst only.

a) i) Compounds with the same molecular formula but different arrangement of atoms/structural formula/structure ii) but-2-ene iii)(CH3)CH=CH(CH3) + HBr -> CH2CHBrCH2CH3 iv) secondary

Alkenes, alcohols, and esters are three families of organic compounds with many commercial uses. a) i) State the meaning of the term structural isomers ii) X is an isomer of C4H8 and has the structural formula shown below. Apply IUPAC rules to name this isomer. Decide the structural formulas of two other isomers of C4H8. iii) State the balanced chemical equation for the reactions of X with HBr to form Y. iv) Y reacts with aqueous sodium hydroxide, NaOH (aq), to form an alcohol, Z. Identify whether Z is a primary, secondary, or tertiary alcohol.

Hydrogen bonding in butan-1-ol therefore it has a stronger attraction compared to the dipole-dipole attractions in butanal

Based on types of intermolecular dories present, explain why butan-1-ol has a higher boiling point than butanal.

The oxidation of a secondary alcohol is a one-step process that produces a ketone. After a ketone is produced, no further oxidation is possible as the carbon of the ketone has no more hydrogen attached to it. Butanone

Butan-2-ol is heated with acidified K2Cr2O7 using a reflux column. Outline the reaction process and give the IUPAC name of the final product

Double bond/alkene; orange/brown/red/yellow to colourless

Compound X (contains double bond) is produced by bacteria living in human armpits and its though to be partly responsible for unpleasant body smells. a) Bromine water can be used to test for the presence of one of the functional groups in X. Identify this functional group and describe the coloraturas change observed

a) nC = 81.7/12.01 = 6.80 and nH = 18.3/1.01 = 18.1; ration of 1:2.67; C3H8 b) C3H8 c) i) Bromine; UV ii) Initiation: Br2 -> (UV) 2Br• Propagation: Br• + RCH3 -> RCH2• + HBr RCH2• + Br2 -> RCH2Br + Br• Termination: Br• + Br• -> Br2

Consider the following sequence of reactions RCH3 -> RCH2Br -> RCH2OH -> RCOOH RCH3 is an unknown alkane in which represents an ally group a) The alkane contains 81.7% by mass of carbon. Determine its empirical formula, showing your working b) Equal volumes of carbon dioxide and the unknown alkane are found to have the same mass, measure to an accuracy of two significant figures, at the same temperature and pressure. Deduce the molecular formula of the alkane. c) i) State the reagent and condition need for the first reaction d) Reaction 1 involves a free-radical mechanism. Describe the stepwise mechanism, by giving equations to represent the initiation, propagation and termination steps

a. The empirical formula* of a compound gives the simplest whole-number ratio of atoms present in a molecule, e.g. CH3. b. The molecular formula gives the actual number of atoms present in a molecule, e.g. C2H6. c. Full structural formulae show all bonds between all atoms, e.g. d. Condensed structural formulae are like full structural formulae − the difference is that they do not show the bonds between the atoms, e.g. CH3CH3.

Define the following terms: a. Empirical formula b. Molecular formula c. Full structural formula d. Condensed structural formula

Alkenes are more reactive than alkanes due to their double C=C bond that is electron-rich and can break open to allow for addition reactions. When bromine water is mixed with ethene, an addition reaction will take place: Bromine water (a solution of Br2 in water) has a brown-reddish color. Since Br2 is used in the reaction, its concentration will decrease so that the color of the mixture will fade (and eventually disappear). When bromine water is mixed with ethane, no reaction will take place. The color of the mixture will not change.

Describe how bromine water can be used to distinguish between ethane and ethene.

Esters are formed when carboxylic acids react with an alcohol in the presence of sulphuric acid as catalyst.

Describe how ethyl propanoate can be produced

CH3CH(CH3)CH(CH3)CH2CH3

Draw the full structural formula and the condensed structural formula of 2,3-dimethylpentane.

i) same functional group / same general formula; difference between successive members is CH2; similar chemical properties; gradually changing physical properties ii) adding bromine water ethene -> brown/yellow to colourless / decolourizes bromine water ethane -> doesn't change colour iii) C2H4 + HBr -> C2H5Br; C2H6 + Br2 -> C2H5Br + Her

Ethene belongs to the homologous series of the alkenes. i) State three features of a homologous series ii) Describe a test to distinguish ethene from ethane, including what is observed in each case iii) Bromoethane can be produced either from ethane or from ethene. State the equation for each reaction.

Initiation: Cl2 -> (UV) 2Cl• Propagation: Cl• + CH4 -> CH3• + HCl CH3 + Cl2 -> CH3Cl + Cl• Termination: Cl• + Cl• -> Cl2

Explain, using equations, the following steps in the free-radical mechanisms of the reaction of methane and chlorine Initiation: Propagation: Termination:

pentan-2-ol, but-2-ene

Give the IUPAC name for the compounds below.

B. C(CH3)3Br

Halogenoalkanes react with dilute sodium hydroxide to form alcohols. Which of the four isomers of bromobutane will react the fastest under the same conditions? A. CH3CH2CH2CH2Br B. C(CH3)3Br C. CH3CHBrCH2CH3 D. CH3CH(CH3)CH2Br

a) Initiation: Cl2 -> 2Cl• Essential condition: UV/Sunlight Propagation: Cl• + R-H -> HCl + R• / R• + Cl2 -> RCl + Cl2 Termination: Cl• + Cl• -> Cl2 b) three

Hexane reacts with chlorine to form different products. The reactions can be represented by the following equations, where R is an alkyl chain. R-H + Cl2 -> R-Cl +HCl a) Describe the stepwise mechanism by giving one equation for each step and state the essential condition in the initiation step A) Initiation B) Essential condition C) Propagation D) Termination b) Deduce the number of straight-chain structural isomers produces with the molecular formula C6H13Cl

A. 2

How many structural isomers are there with the molecular formula C4H10? A. 2 B. 3 C. 4 D. 5

B. H2

Hydrogenation of unsaturated fats produces saturated fats which are the major constituents of dairy products. Which of the following reagents is used in the hydrogenation process? A. HBr B. H2 C. H3PO4 D. Cl2

Carboxamide, phenyl, carboxyl, hydroxyl

Identify four functional groups

a) Look it up b) i) C5H12 + Br2 -> C3H7HBr; UV ii) C3H6 + Br2 -> C3H6Br2 iii) Propane -> free radical substitution Propene -> electrophile addition

Propane and propene are members of different homologous series. a) Draw the full structural formulas for both propane and propene b) Both propane and propene react with bromine i) State an equation and the condition required for the reaction of 1 mol of propane and 1 mol of bromine ii) State an equation for the reaction of 1 mol of propene with 1 mol of bromine iii) State the type of reaction with bromine for each

but-1-ene

State the IUPAC name for the compound with the condensed structural formula: CH2CHCH2CH3

Carboxylic acid

State the class that the following organic molecule belongs to:

Alkynes (This homologous series, the alkynes, is the one in which the molecules contain a carbon-carbon triple bond; the series has the general formula CnH2n - 2. Ethyne is the first, and simplest, member of the series.)

State the name of the homologous series to which ethyne (C2H2) belongs.

A. Amine

The -NH2 group is the functional group of which homologous series? A. Amine B. Nitrile C. Ester D. Amide

a) methylpropene b) i) orange/brown/red/yellow to colourless ii) 1,2-dibromo-2-methlypropane

The alkenes are an example of a homologous series a) State the name of the alkene shown b) Bromine water, Br2(aq) can be used to distinguish between the alkanes and the alkenes . i) Describe the coloraturas change observed when the alkene shown in part (a) is added to bromine water ii) Draw the structural formula and state the name of the product formed

a) butan-2-ol b) CH3CH2CH2CH2OH; (CH3)2CHCH2OH

The following diagram shows the three-dimensional structure of a molecule. a) Apply IUPAC rules to state the name of this molecule b) Deduce the structural formula of two isomers of the molecule above with the same functional group

i) butane < propanal < propan-1-ol butane has van der Waals forces; propanal has dipole-dipole attractive forces; propan-1-ol has hydrogen bonding ii) butane is least soluble because it can't form hydrogen bonds/attractive forces with water molecules

Three compounds with similar relative molecular masses are butane, propanal, propan-1-ol. i) List the three compounds in order of increasing boiling point and explain the differences in their boiling points ii) Predict, with an explanation, which of the three compounds is least soluble or miscible in water

C. 3,3,4-trimethylhexane (A branch cannot be assigned to the last carbon in a chain: it would be part of the longest carbon chain. 3,4,4-trimethylhexane is not the correct answer: by numbering from the opposite end of the butane chain the designations for the methyl groups become 3,3,4.)

What is the IUPAC name for the molecule with the following condensed structural formula? CH3CH2C(CH3)2CH(CH3)CH2CH3 A. 4-ethyl-3,4,4-trimethylbutane B. 3,4,4-trimethylhexane C. 3,3,4-trimethylhexane D. 4-ethyl-3,3,4-trimethylbutane

Pentylbutanoate

What is the IUPAC name of the ester when pentan-1-ol and butanoic acid react.

C. 2,2-dimethylbutane

What is the IUPAC name of the following hydrocarbon? A. hexane B. 2-methylpentane C. 2,2-dimethylbutane D. ethylbutane

1.5 bond (The sum of the individual bonds orders is 1+2+1+2+1+2 = 9 (assuming that benzene has alternating single and double bonds as in the Kekule structure). There are six bonding positions in benzene, therefore, the bond order is: 9/6 = 1.5)

What is the bond order of the carbon to carbon bonds in benzene, C6H6?

A. To break the bond between the chlorine atoms in the chlorine molecule

What is the function of UV radiation during the reaction between chlorine and methane? A. To break the bond between the chlorine atoms in the chlorine molecule B. To dissociate the chlorine molecules into ions C. To increase the temperature of the mixture D. To break C−H bonds in the methane molecules

Positional (Here, the only thing that has changed is the position of the hydroxyl (alcohol) group, the chain remains the same with all of the carbons bonded in a straight chain. Position (positional) isomerism is a form of structural isomerism.)

What kind of isomers are pentan-2-ol and pentan-3-ol? Answer with one word only.

Homologous series

What name is given to a series of compounds which have the same functional group, show a trend in physical properties and have the same general formula? Answer with two words only(____________ series).

D. I, II and III

Which can react to form addition polymers? I. H2C=CH(CH3) II. H2C=CH2 III. H2C=CHCl A. I and II only B. I and III only C. II and III only D. I, II and III

C. Primary alcohols can be formed by the reduction of carboxylic acids.

Which is a correct statement about alcohols? A. Secondary alcohols are formed by the oxidation of ketones. B. Tertiary alcohols can be readily oxidised to carboxylic acids. C. Primary alcohols can be formed by the reduction of carboxylic acids. D. Secondary alcohols can be oxidised to form aldehydes.

D. CH3CH(CH3)CHBrCH3

Which is the correct formula for 2-bromo-3-methylbutane? A. CH3CBr2CH(CH3)CH3 B. CH3CHBrCH2CH(CH3)2 C. CH3CBr2C(CH3)2 D. CH3CH(CH3)CHBrCH3

D. CH3CH2CHBrCH3

Which is/are the products when but-2-ene reacts with hydrogen bromide? A. CH3CH2CHBrCH3 + H2 B. CH3CHBrCHBrCH3 + H2 C. CH3CH2CH2CH2Br D. CH3CH2CHBrCH3

B. CO and H2O

Which of the following are the correct products when octane (C8H18) undergoes incomplete combustion? A. CO2 and H2O B. CO and H2O C. CO and H2 D. CH4 and H2

A. methanol and propanoic acid

Which pair of compounds can be used to prepare C2H5COOCH3? A. methanol and propanoic acid B. ethanol and ethanoic acid C. propan-1-ol and methanoic acid D. methanol and ethanoic acid

Propanone (Both compounds are ketones and so both have dipole-dipole forces between their molecules. The factor that determines their volatility is molar mass. Volatility decreases with increasing molar mass as this increases the strength of the London dispersion forces between the molecules, so more energy is needed to make the liquid evaporate. Pentan-3-one has the highest molar mass and is the least volatile.)

Which of the following compounds has the higher volatility: propanone or pentan-3-one? Answer with propanone or pentan-3-one.

A. I and II only

Which of the following contribute significantly to the low reactivity of alkanes? I. The relatively strong C-H bond II. The very low polarity of the C-H and C-C bonds III. The tetrahedral shape of the molecules A. I and II only B. I and III only C. II and III only D. I, II and III

B. CH3• + Cl• → CH3Cl

Which of the following is an example of a termination step in the free-radical substitution reaction of an alkane? A. CH4 + Cl• → CH3• + HCl B. CH3• + Cl• → CH3Cl C. Cl2 → Cl• + Cl• D. CH3• + Cl2 → CH3Cl + Cl•

B. 3-methylbutane (Branches of the longest, continuous carbon chain are given the lowest number designations possible. A sketch of 3-methylbutane reveals that it is structurally identical to 2-methylbutane, therefore, the name 2-methylbutane should be used.)

Which of the following is not considered a structural isomer of C5H12? A. Pentane B. 3-methylbutane C. 2-methylbutane D. 2,2-dimethylpropane

A. Each member in the homologous series has the same general formula, CnH2n (The alkane chain consists of CH2 units; however, bonding dictates that each end of the chain must terminate with a hydrogen atom. Therefore, the general formula for the homologous series of alkanes is C2H2n+2. By contrast, C2H2n could represent a homologous series of alkenes.)

Which of the following is not true for a homologous series of alkanes? A. Each member in the homologous series has the same general formula, CnH2n B. Each member in the homologous series has similar chemical properties C. The homologous series shows a gradual change in physical properties D. The formula of each member in the homologous series differs from the others by the number of CH2 units present

C. II and III only

Which of the following reactions can alkenes undergo? I. Nucleophilic substitution II. Combustion III. Hydrogenation A. I and II only B. I and III only C. II and III only D. I, II and III

D. C8H18 (As the molar mass increases, the strength of the London dispersion forces between the molecules also increases, which results in an increase in boiling point. C8H18 has the highest molar mass, therefore, it has the highest boiling point.)

Which of the following straight-chain alkanes has the highest boiling point? A. C5H12 B. C3H8 C. CH4 D. C8H18

A. I and II only

Which of the following will undergo reaction with sodium hydroxide solution via an SN2 mechanism? I. CH3CH2CH2CH2Br II. CH3CH(CH3)CH2Br III. C(CH3)3Br A. I and II only B. I and III only C. II and III only D. I, II and III

A. CH3CH2CH3 (Propanal is roughly 500 times more soluble in water than propane, due to dipole-dipole attractions between the carbon-oxygen double bond and the hydrogen-oxygen single bonds in water. Both 1-propanol and propanoic acid are capable of hydrogen bonding with water, making them both highly soluble in it. Propane, a non-polar molecule, has the lowest solubility in water.)

Which of the following would be expected to have the lowest solubility in water? A. CH3CH2CH3 B. CH3CH2CHO C. CH3CH2CH2OH D. CH3CH2COOH

C. It involves homolytic bond fission and Cl• radicals

Which of these statements about the reaction between methane and chlorine is correct? A. It involves heterolytic bond fission and Cl- ions B. It involves heterolytic bond fission and Cl• radicals C. It involves homolytic bond fission and Cl• radicals D. It involves homolytic bond fission and Cl- ions

Pentanol (Both have an -OH group so will have hydrogen bonding of the same approximate strength. However, as pentanol is larger, its London dispersion forces will be stronger so more energy will be required to make it boil.)

Which of these two molecules has a higher boiling point: butanol or pentanol?

A. 2,3-dimethylbutane (A methyl group cannot receive a number designation of "1"; this indicates that it is part of the longest carbon chain. 1,3-dimethylbutane should be named 2-methylpentane. The branches must always be given the lowest possible number designations: 3,3-dimethylbutane should be named 2,2-dimethylbutane. A methyl group cannot receive a number designation at the end of the longest carbon chain; it would be considered part of that chain. Therefore, 1,4-dimethylbutane should be named hexane.)

Which one of the following is an accepted IUPAC name for a compound with the molecular formula C6H14? A. 2,3-dimethylbutane B. 1,3-dimethylbutane C. 3,3-dimethylbutane D. 1,4-dimethylbutane

Initiation: UV light breaks the bond in the bromine molecule (photochemical homolytic fission) to produce two bromine radicals. In initiation steps the number of free radicals increases. Propagation: A bromine free radical reacts with methane to produce a methyl radical and hydrogen bromide. Propagation: In a second propagation step a methyl radical (produced in the first propagation step) reacts with a bromine molecule to produce bromomethane and a bromine radical. CH3Br can continue to react through similar propagation steps to form CH2Br2, CHBr3 and eventually CBr4. Termination: Free radicals react with each other to form molecules. Since the radicals are much more reactive than the molecules, the reaction stops when there are no more radicals.

Write and explain the steps of the free radical substitution mechanism between methane and bromine in the presence of UV light.