organic chemistry: Alkenes and Alkynes – quiz 6

(36) The volume of gases produced from the thermal cracking reaction  ………… are greatest

(a) C₆H_14(g) >>> 3C₂H_4(g) + H_2(g).

(b)C₈H_18(g) >>> 2C₃H_8(g) + C₂H_{2 (g)}

(c) C₁₀H_22(g)  >>> C₈H_18(g) + C₂H_4(g)

(d) C₁₂H_26(g)   >>> C₈H_18(g) + 2 C₂H_4(g)

(34) The gas which is obtained from thermal catalytic cracking of octadecane C₁₈H₃₈ is  ……….

(a) CO₂ 

(b) C₁₈H₃₆  

(c) C₃₆H₇₄ 

(d) C₉H_18.

(33) Both of ………. are obtained from the thermal catalytic cracking of octane.

(a) hexane and ethane

(b) Butene and butane.

(c) heptane and methane

(d) propane and pentane

(32) Chlorine reacts with methane gas forming …………. in the presence of ultraviolet rays.

(a) chloromethane and hydrogen

(b) chloromethane and Hydrogen chloride

(c) dichloromethane and hydrogen

(d) dichloromethane and trichloromethane

31 ) Freons are used in air conditions and fridges, because they are ………..

(a) cheap.

(b) liquefied easily.

(c) non-poisonous and don't cause erosion.

(D) (a), (b) and (c).

(30) The molecular formula of chloroform is ………..

(a) CCl₄  

(b) CH₂Cl₂  

(c) CH₄  

(d) CHCI₃.

(29) Alkanes react with halogens in the presence of ultraviolet rays by

(a) elimination.

(b) condensation.

(c) Substitution.

(d) reduction.

(28) The gas which burns in air forming two gases; one of them turns the clear limewater turbid and the other turns the anhydrous <a href="https://gogoacademy.net/science-prep-1-final-revision/">copper</a> (II) sulphate into blue is …….

(a) Ethane.

(b) carbon monoxide

(c) hydrogen

(d) gasoline

 (27) Alkanes which contain more than 17 carbon atoms are exist in state.

(a) Solid 

(b) liquid 

(c) vapour 

(d) gaseous

(26) The boiling point of butane is less than that of ……….

(a) ethane.

(b) propane.

(c) methane.

(d) Hexane

(25) In hot countries, the fuel cylinders contain large amount of ………  gas.

(a) ethane

(b) propane 

(c) Butane 

(d) pentane

(24) In cold countries, the fuel cylinders contain high amount of

(a) methane

(b) ethane  

(c) Propane.

(d) butane

(23) Which of the following compounds have the highest boiling point?.......

(a) Normal Hexane..

(b) Normal pentane.

(c) 2,2-dimethyl propane.

(d) 2-methyl butane

(22) Gasoline consists of compounds which contain  …….. carbon atoms

(a) from 1:4  

(b) from 4:5

(c) from 5:17.  

(d) more than 17

(21) Soda lime is a mixture of ……..

(a) caustic soda and calcium carbonate

(b) caustic soda and Quick lime

(c) sodium carbonate and quick lime

(d) caustic soda and slaked lime

(20) The dry distillation of anhydrous sodium acetate with soda lime produces ……

(a) ethane. 

(b) Methane. 

(c) propane

(d) butane

(19) The boiling point of ……….. is less than that of the other three compounds

(a)C₂H_{6 .}      

(b) CH₃(CH₂)₂CH₃ 

(c)CH₃(CH₂)₄CH₃

(d)C₈H₁₈

(18) With increasing  the molecular <a href="https://gogoacademy.net/science-prep-1-final-revision/">mass</a> in alkanes, the property ……….  doesn't increase

(a) boiling point

(b) Ability to burn

(c) melting point

(d) viscosity

(17) Complete burning of 1 mole of ……….. produces 3 mole of CO2, and 4 moles of H2O

(a) C₃H_8.

(b) C₃H₄

(c) C₂H₄

(d) C₂H₂

(16) 1 L of gas …… reacts with 5 L of O₂ , at STP

(a)CH₄  

(b) C₂H₆

(c) C₃H₈.  

(d)C₄H₁₀

(15) Burning of 20 cm³ of gas  …… in an excess of O₂

At STP produces 60 cm3 of CO₂

6. a) C₃H₆.

(b) C₄H₁₀

(c) C₆H₁₂

(d) C₆H₁₄

(14) The gas which causes the decay of the <a href="https://gogoacademy.net/science-preparatory-2-final-revision/">ozone layer</a> is

(a) CH₃CH₂CH₃

(b) CH₃CHCI₂

(C) CH₃OCH₃

(D) CF₂Cl₂

(13) 2-methyl pentane is considered the isomer of the compound ………….

(a) 2-methyl butane. 

(b) (2,2-dimethyl Butane

(c) 2,2-dimethyl pentane  

(d) 2,2-dimethyl propane

(17) 1,2-dibromoethane is not formed, when hydrogen bromide reacts with ethyne.

why?

(16) Sulphuric acid plays an important role in the addition reaction of water to ethene.

why??

(15) Bromine dissolved in carbon tetrachloride is not used to differentiate between ethene and ethyne.

why??

(14) Ethene reacts by addition in one step, whereas Ethyne reacts in two steps.

(13) Oxyacetylene flame is used in cutting and welding metals.

(12) Before the collection of ethyne gas prepared by dropping water on calcium carbide, it must be firstly passed over <a href="https://gogoacademy.net/science-prep-1-final-revision/">copper</a> sulphate solution in sulphuric acid.

why??

(11) Alkynes are very active compounds.

Why?

(10) Ethylene glycol is used as an antifreeze substance in car radiators in cold areas.

Why?

(9) The violet color of potassium permanganate in alkaline medium is discharged when it reacts with ethene.

Why?

(8) The hydration reactions of alkenes should proceed in the presence of a strong acid.

Why?

(7) On adding hydrogen bromide to vinyl bromide, 1,2-dibromoethane is not formed

Why?

(6) On adding hydrogen bromide to propene, 1-bromopropane is not formed.

Why??

(5) When bromine dissolved in carbon tetrachloride is added to ethene, the red colour of  bromine is discharged.

Why?