ACSBR 20B Molecular Structures (Extensions) - Assignment ANS

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ANSWERS ( ) Class: SEC 4 OC: MOLECULAR STRUCTURES (EXTENSIONS) – ASSIGNMENT ALEX LEE/2010 PAGE 1 OF 6 PURE Multiple-Choice Questions [20 Marks] TOTAL SCORE / 30 Write in your selected answer for the multiple-choice questions in the boxes provided. 1 2 3 4 5 6 7 8 9 10 B A B C A B C C A D 11 12 13 14 15 16 17 18 19 20 C A D A A B B C C C 1. Which of the following statements about isomers is false? A Isomers have the same relative molecular mass. B Isomers have the same strength of intermolecular forces. C Isomers may have the same chemical properties as each other. D Isomers have the same percentage composition of elements. 2. Two molecules are isomers. It follows that these two molecules A contain the same elements. C have different molecular formulae. B contain the same functional group. D have the same structural formula. 3. Butanoic acid has a formula C4H8O2. It can be concluded that an isomer of this molecule A must be able to react with carbonates. B must combust to form carbon dioxide and water. C must contain the –COOH functional group. D must not contain a C=C bond in its structure. 4. What property do methylpropane and butane not have in common? A combustion products B empirical formula C melting and boiling points D relative molecular mass 5. The smallest alkane to have more than one structural isomer is A butane B ethane C pentane D propane

ALEX LEE/2010 PAGE 2 OF 6 6. How many structural isomers exist for C2H6O? A one B two C three D four 7. Which of the following molecules have the greatest number of structural isomers? A C3H7Cl B C3H6Cl2 C C3H4Cl4 D C3H2Cl6 8. A compound with the formula C4H9F has A 2 isomers. B 3 isomers. C 4 isomers. D 5 isomers. 9. Which, of the four molecules below, is a different structure from the other three molecules? A C B D 10. Which of the following pairs of molecules are not isomers? A and B and C and D and C C Cl Cl H H H Cl C C H H Cl Cl Cl H C C Cl H Cl Cl H H C C H Cl Cl H Cl H C C C H Cl H Cl H H H H C C C H H Cl H H H Cl H C C C H H Cl H H Cl H H C C C H H H Cl H H Cl H C C C Cl H H Cl H H H H C C C H H Cl H Cl H H H C C C H H Cl Cl H H H H C C C Cl H Cl H H H H H

ALEX LEE/2010 PAGE 3 OF 6 11. Three molecules, X, Y and Z, are shown below. molecule X molecule Y molecule Z Which of the following statements are true? A Molecules X and Y have different molecular formula. B Molecules X and Z are isomers of each other. C Molecules X and Z have the same structural formula. D Molecules Y and Z have the same melting and boiling points. 12. The structure of a chloroalkane P is shown below. molecule P Which of the molecules below are identical to P? A C B D 13. Which of the following molecules only exist as one isomer? A C2H4F2 B C2H3F3 C C2H2F4 D C2HF5 C C Cl C H Cl H H H H C H H H C C H C Cl H H H H Cl C H H H C C H C H H H Cl Cl H C H H H C C Cl C H H H H H Cl C H H H C C Cl C H H H H H H C H H Cl C C H C H H H H H H C H H H C C H C H H H H H H C H H H C C H C H H H H H H C H H H

ALEX LEE/2010 PAGE 4 OF 6 14. Two molecules, pentene and cyclopentane, are shown below. pentene cyclopentane Which of the following statements about these two molecules are true? A Pentene and cyclopentane are isomers of each other. B Pentene and cyclopentane have the same chemical properties. C Pentene is a hydrocarbon while cyclopentane is not. D Pentene requires more oxygen for combustion compared to cyclopentane. 15. The diagrams below show five fluoroalkanes with the formula C5H11F. C CCC C H H H H H H HHH HF H C CCC C H H H H H H H H H H H H HHHHHH HF H CC CC CHHH H H H H H H H H F CC CC CHHHHHH H H H H H H H H H H H H H H F CCC C CH H H HHF HHH H H H CCC C C CCC C CH H H H H H HHFHHF HHHHHH H H H molecule 1 molecule 2 molecule 3 C CCC H H H HHH CHHH F H H C CCC H H H H H H HHH CHHH F H H C CCCC H H H H H H FHH H H H C CCCC C CCCC H H H H H H H H H H H H FHHFHH H H H molecule 4 molecule 5 Which two molecules are the same? A molecules 1 and 2 C molecules 3 and 5 B molecules 2 and 4 D molecules 4 and 5 16. Which of the following molecules contain exactly three chlorine atoms? A 1,1,3,3-tetrachlorohexane C 1-chloro-3-fluorobutane B 1-bromo-1,1,2-trichloroethane D 2,3-dichloro-1,3-difluoropentane

ALEX LEE/2010 PAGE 5 OF 6 17. The structure of an organic molecule is shown below. Which of the following names best describe this molecule? A ethylbutane B ethylpentane C methylbutane D propylpropane 18. The structure of an organic molecule is shown below. A ethylbutane B ethylpropane C methylbutane D methylpropane 19. Which of the following molecules is 1,2,2-trichloropropane? A C B D 20. Which of the following pairs of molecules are isomers? A chloromethylpropane and dichloromethylpropane B dichlorobutane and dichloropropane C dimethylpropane and methylbutane D ethylbutane and methylpropane C C C H H H Cl H H Cl Cl C C C H Cl H H H Cl Cl H C C C Cl H Cl H H Cl H H C C C Cl H Cl Cl H H H H C C C H C H H H H H H H C H C H H H H C H H H H C C C H H H H C H H H H C H H H

ALEX LEE/2010 PAGE 6 OF 6 Structured Questions [10 Marks] 21. Ethane can undergo a chemical reaction with chlorine to form gaseous trichloroethane, C2H3Cl3, with hydrogen chloride as a byproduct. This product has two isomers. (a) Construct a chemical equation, including state symbols, for this reaction. [1] C2H6 (g) + 3 Cl2 (g) ⎯→ C2H3Cl3 (g) + 3 HCl (g) (b) Explain what is meant by the term ‘isomers’. [1] Two or more molecules with the same molecular formula, but different structural formula. (c) In the space below, write down the names of the two isomers of trichloroethane and draw their full-structural formula. [4] Isomer #1 Isomer #2 Name: 1,1,1-trichloroethane Name: 1,1,2-trichloroethane Full Structural Formula: Full Structural Formula: (d) Propane can undergo a similar reaction with chlorine to form trichloropropane, C3H5Cl3. How many structural isomers does trichloropropane have? [1] five 22. From the list of names provided below, identify the molecules shown. [3] 1-bromobutan-2-ol 2-bromopropanoic acid 3-methylbut-1-ene 1-methylpent-2-ene 1-bromobutan-2-ol butan-2-ol CHC H H C H BrO OH CHC H H C H BrO OH C CC HC H H H H CHH H H H C CC HC H H H H CHH H H H C CC H HO HH C H H H H H H C CC H HO HH C H H H H H H 2-bromopropanoic acid 3-methylbut-1-ene butan-2-ol END C C H Cl Cl Cl H H C C H Cl Cl H Cl H