Chemistry_2019_STPM term 3_Objectives

The bonding in toluene involves the following orbitals except

• s

• sp

• sp²

• sp³

Answer explanation

The H atom uses its 1s orbital to overlap with the sp³ orbital to form C-H bond in CH₃. sp orbital is involved only in the formation of carbon-carbon triple bond, C ≡ C.

When 15 cm³ of a gaseous hydrocarbon completely burnt in oxygen, 45 cm³ of carbon dioxide and 60 cm³ of water vapour formed at standard pressure and temperature. Which is true about the hydrocarbon?

• Has primary, secondary and tertiary carbon atoms

• Its chemical formula is C₃H₆

• Forms propene on cracking

• Has no isomers

Answer explanation

The structural formula of progesterone is shown in the diagram. Which is true about the properties of progesterone?

• Optically inactive

• Reduces to a primary alcohol

• Shows a negative result with iodoform test

• Undergoes free radical substitution with chlorine in UV light

Answer explanation

Which molecule does not show geometrical isomerism?

• 1-Bromo-2-chloropropene

• 1-Chloro-2-methylcyclopentane

• 1,1-Dichloro-2-methylpropene

• 1, 2-Dichlorocyclobutane

Answer explanation

X reacts with hot acidified potassium manganate (Ⅶ) solution to produce two organic compounds. What is X?

• CH₃CH=CH₂

• (CH₃)₂C=CH₂

• (CH₃)₂C=C(CH₃)₂

• (CH₃)₂C=CHCH₃

Answer explanation

The reaction scheme for the preparation of benzyl 4-methylbenzoate is shown in the diagram. Which reagents are used in Ⅰ and Ⅱ ?

• 
• 
• 
• 

Answer explanation

Chlorofluoroalkanes are suitable to be used as aerosol propellant because of their inertness. Which factor contributes to their inertness?

• High molecular weight

• Non-flammable

• Strong covalent bond

• Low boiling point

Answer explanation

Which is true about the reaction between 1-butanol and hydrogen chloride?

• Occurs at room temperature

• Involves cleavage of RO—H bond

• Involves the formation of a primary carbocation

• Forms organic product that is soluble in water

Answer explanation

Which organic compound forms white fumes with PCl₅, forms bubbles with Na₂CO₃ and decolourises acidified KMnO₄ solution?

• HCOOH

• CH₃COOH

• CH₃CH₂OH

• C₆H₅OH

Answer explanation

It contains the -OH group (white fumes with PCl₅).

It has -COOH group (form bubbles with Na₂CO₃).

It can be oxidised (decolourisation of KMnO₄). The two acids that can be oxidised are HCOOH and H₂C₂O₄.

Which is the product of the reaction between phenylmethanol and ethanoyl chloride?

• C₆H₅CH₂COCl

• CH₃COOC₆H₅

• C₆H₅CH₂COOCH₃

• CH₃COOCH₂C₆H₅

Answer explanation