EmSAT Chemistry 5 — Questions and Answers
Question 1: Which type of isomerism is exhibited by cis-2-butene and trans-2-butene?
- Chain isomerism
- Positional isomerism
- Geometric (cis-trans) isomerism (Correct answer)
- Optical isomerism
Correct answer: Geometric (cis-trans) isomerism
Cis- and trans-2-butene differ in the spatial arrangement of groups around the C=C double bond, making them geometric isomers.
Question 2: Which of the following correctly describes a buffer solution?
- A solution that contains only a strong acid
- A solution that resists changes in pH on addition of small amounts of acid or base (Correct answer)
- A solution with a pH of exactly 7
- A solution that neutralises all acids added to it
Correct answer: A solution that resists changes in pH on addition of small amounts of acid or base
A buffer solution contains a weak acid and its conjugate base (or weak base and conjugate acid) that absorb added H⁺ or OH⁻ ions, keeping pH nearly constant.
Question 3: In the periodic table, which trend is observed for ionisation energy across Period 3 (Na to Ar)?
- Generally decreases
- Remains constant
- Generally increases (Correct answer)
- First increases then decreases uniformly
Correct answer: Generally increases
Across a period, nuclear charge increases while shielding remains roughly constant, so electrons are held more tightly and ionisation energy generally increases.
Question 4: What type of reaction produces a polymer from many alkene monomers?
- Condensation polymerisation
- Addition polymerisation (Correct answer)
- Hydrolysis
- Saponification
Correct answer: Addition polymerisation
In addition polymerisation, the C=C double bonds of alkene monomers open and join together without losing any small molecules.
Question 5: A sample of gas occupies 2.0 L at 300 K and 100 kPa. What volume does it occupy at 600 K and 100 kPa?
- 1.0 L
- 2.0 L
- 4.0 L (Correct answer)
- 8.0 L
Correct answer: 4.0 L
At constant pressure, Charles's Law gives V₁/T₁ = V₂/T₂; (2.0/300) = V₂/600, so V₂ = 4.0 L.
Question 6: Which of the following best explains why diamond has a very high melting point?
- It is made of carbon atoms held by weak van der Waals forces
- Each carbon atom forms four strong covalent bonds in a giant 3D network (Correct answer)
- It contains ionic bonds between carbon atoms
- It is a metal with strong metallic bonding
Correct answer: Each carbon atom forms four strong covalent bonds in a giant 3D network
In diamond, each carbon is covalently bonded to four others in a rigid tetrahedral lattice, requiring enormous energy to break.
Question 7: Which reagent is used to test for the presence of starch, and what colour change confirms a positive result?
- Benedict's solution — blue to brick-red
- Fehling's solution — blue to orange
- Iodine solution — yellow-brown to blue-black (Correct answer)
- Biuret reagent — blue to purple
Correct answer: Iodine solution — yellow-brown to blue-black
Iodine solution turns blue-black in the presence of starch due to iodine molecules entering the helical structure of amylose.
EmSAT Chemistry 5
Which type of isomerism is exhibited by cis-2-butene and trans-2-butene?