Organic [Alkanes, Alkenes, Haloalkanes]

Using integers, what is the smallest sum of all the coefficients when the equation for the complete combustion of octane, C8H18 in oxygen is correctly balanced?

• 50

• 30

• 31

• 61

Which factors contribute to the explanation as to why alkanes are not very reactive?

I. Unlike the other elements in group 14, carbon cannot expand its octet.

II. C−H and C−C bonds are relatively strong compared to other covalent single bonds.

III. Alkanes either are non-polar or have very low polarity.

• I only

• I and II only

• I, II and III

• III only

Methane reacts with chlorine in the presence of ultraviolet light to form chloromethane and hydrogen chloride. What is the function of the ultraviolet light?

• It breaks the C−H bond in methane homolytically.

• It breaks the Cl−Cl bond in chlorine heterolytically.

• It breaks the C−H bond in methane heterolytically.

• It breaks the Cl−Cl bond in chlorine homolytically.

Which is a propagation step in the substitution reaction between ethane and bromine in the presence of ultraviolet light?

• H₃C−CH₂· + Br· → H₃C−CH₂Br

• H3C−CH2· + H3C−CH2· → H3C−CH2−CH2−CH3

• H₃C−CH₃ + Br· → H₃C−CH₂· + HBr

• Br₂ → Br· + Br·

What product will be formed when water is reacted with ethene in the presence of a catalytic amount of concentrated sulfuric acid?

• ethanal

• ethanoic acid

• ethanol

• 1,2-ethanediol

Under high pressure alkenes can be polymerized to give addition polymers.

Polystyrene is an addition polymer.

• C₆H₅CH=CH₂

• C₆H₆CH₂CH=CH₂

• C₆H₅CH₂CH=CH

• C₆H₅CH₂CH₃

Which product will be formed when but-2-ene reacts with hydrogen bromide?

• 2-bromobutane

• 3-bromobutane

• 1,2-dibromobutane

• 2,3-dibromobutane

What simple test can be used to distinguish a liquid alkene from a liquid alkane?

• Habour process

• Shine ultraviolet light on each liquid separately.

• Burn them separately and pass the gaseous products through calcium hydroxide solution (lime water).

• Shake each one with a small amount of bromine water.

Which factors help to explain why halogenoalkanes are generally more reactive than alkanes?

I. The molecules of halogenoalkanes are more polar than molecules of alkanes.

II. All C−halogen bonds are weaker than C−C and C−H bonds.

III. All the halogens are more electronegative than hydrogen and carbon.

• II and III only

• I and III only

• I, II and III

• I and II only

Methane (boiling point (− 161 oC) and tetrafluoromethane (boiling point − 128 oC) are both greenhouse gases. The C−H bond enthalpy is 414 kJ mol−1 and the C−F bond enthalpy is 492 kJ mol−1.

Which statements about methane and tetrafluoromethane are correct?

I. The molecules of both methane and tetrafluoromethane have a tetrahedral structure.

II. Methane is more reactive chemically than tetrafluoromethane.

III. Tetrafluoromethane is considerably more polar than methane.

• II and III only

• I and III only

• I, II and III

• I and II only