basic concepts questions

Topics: Structural formula, Chemical formulas, Isomer Pages: 6 (946 words) Published: March 14, 2014
1.Predict the molecular formula of an alkane with 13 carbon atoms. .................................................................................................................................. [Total 1 mark]

2.Bromobutane, CH3CH2CH2CH2Br, can be reacted with hot aqueous sodium hydroxide to prepare butan-1-ol.
CH3CH2CH2CH2Br + OH– → CH3CH2CH2CH2OH + Br–
A student reacted 8.72 g of bromobutane with an excess of OH–. The student produced 4.28 g of butan-1-ol. (i)Calculate the amount, in mol, of CH3CH2CH2CH2Br reacted.
CH3CH2CH2CH2Br, Mr = 136.9

............................................... mol
[1]

(ii)Calculate the amount, in mol, of CH3CH2CH2CH2OH produced.

............................................... mol
[2]

(iii)Calculate the percentage yield.
Quote your answer to three significant figures.

.................................................. %
[1]
[Total 4 marks]

3.But-1-ene is just one isomer with the molecular formula C4H8.
Using C4H8 as your example, describe and explain what is meant by structural isomerism and cis-trans isomerism.
Include diagrams in your answer.
In your answer you should make clear how each type of isomerism is related to structural features.
(Allow one lined page).
[Total 7 marks]

4.Cylcohexane and cyclohexene are both cyclic hydrocarbons.

cyclohexane cyclohexene
(i)What is the molecular formula of cyclohexene? ............................................. [1]

(ii)What is the empirical formula of cyclohexene? .............................................. [1]
(iii)Calculate the percentage, by mass, of carbon in cyclohexene. Give your answer to two significant figures.

answer ...............................................
[2]
[Total 4 marks]

5.Halogenoalkanes are used in the production of pharmaceuticals, polymers and flame retardants. 1-Bromo-2-methylpropane is used in the production of ibuprofen and can be prepared from the reaction between 2-methylpropan-1-ol and HBr.

(CH3)2CHCH2OH + HBr ® (CH3)2CHCH2Br + H2O
A student reacted 4.44 g of 2-methylpropan-1-ol with an excess of HBr. The student produced 5.48 g of 1-bromo-2-methylpropane. (i)Calculate the number of moles of (CH3)2CHCH2OH used.
answer …………………… mol
[2]

(ii)Calculate the number of moles of (CH3)2CHCH2Br collected. (CH3)2CHCH2Br, Mr =137
answer …………………… mol
[1]
(iii)Calculate the percentage yield. Quote your answer to three significant figures. answer ……………………
[1]
[Total 4 marks]

6.In this question, one mark is available for the quality of use and organisation of scientific terms. Name and give examples of the types of isomerism in compounds with formula C4H8. Explain how each type of isomerism arises. [8]

Quality of Written Communication [1]
[Total 9 marks]

7.Propane, C3H8, is used in the reaction sequence shown below.

(a)The reaction sequence shows several important reaction mechanisms. Select from reactions 1 to 4, the reaction that shows (i)free radical substitution,reaction ..........
[1]
(ii)electrophilic addition,reaction ..........
[1]
(iii)elimination,reaction ..........
[1]

(b)In reaction 2, the aqueous OH– acts as a nucleophile.
(i)State what is meant by the term nucleophile.
................................................................................................................ [1]

(ii)Complete, with the aid of curly arrows, the mechanism involved in reaction 2. Show any relevant dipoles. H3C ¾ CH2 ¾ CH2 ¾ Cl H3C ¾ CH2 ¾ CH2 ¾ OH+.......... OH–
[4]

(c)Compounds B and D are structural isomers of each other.
(i)State what is meant by the term structural isomers.
................................................................................................................ ................................................................................................................ [2]

(ii)Draw the skeletal...
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