EmSAT Chemistry 4 — Questions and Answers
Question 1: What is the IUPAC name of the compound CH₃CH₂CH(OH)CH₃?
- 1-butanol
- 2-butanol (Correct answer)
- Butan-1-ol
- Butanal
Correct answer: 2-butanol
The hydroxyl group is on carbon 2 of a four-carbon chain, making this butan-2-ol, commonly written as 2-butanol.
Question 2: Which gas is produced when dilute hydrochloric acid reacts with zinc metal?
- Oxygen
- Chlorine
- Carbon dioxide
- Hydrogen (Correct answer)
Correct answer: Hydrogen
Zinc displaces hydrogen from the acid: Zn + 2HCl → ZnCl₂ + H₂, releasing hydrogen gas.
Question 3: The half-life of a radioactive isotope is 10 days. What fraction of the original sample remains after 30 days?
- 1/2
- 1/4
- 1/8 (Correct answer)
- 1/16
Correct answer: 1/8
30 days = 3 half-lives, and (1/2)³ = 1/8 of the original sample remains.
Question 4: Which of the following molecules has a trigonal planar geometry?
- NH₃
- H₂O
- BF₃ (Correct answer)
- CH₄
Correct answer: BF₃
BF₃ has three bonding pairs and no lone pairs around boron, giving a trigonal planar shape with 120° bond angles.
Question 5: During the electrolysis of aqueous copper(II) sulfate using copper electrodes, what happens at the anode?
- Copper is deposited
- Oxygen gas is released
- Copper dissolves into solution (Correct answer)
- Hydrogen gas is released
Correct answer: Copper dissolves into solution
The copper anode undergoes oxidation (Cu → Cu²⁺ + 2e⁻), dissolving into the solution and replenishing Cu²⁺ ions.
Question 6: Which functional group is present in an ester?
- –OH
- –COOH
- –COO– (Correct answer)
- –CHO
Correct answer: –COO–
Esters contain the –COO– (carboxylate ester) linkage, formed when a carboxylic acid reacts with an alcohol.
Question 7: What is the molar concentration of a solution made by dissolving 5.85 g of NaCl (M = 58.5 g/mol) in 500 cm³ of water?
- 0.1 mol/L
- 0.2 mol/L (Correct answer)
- 1.0 mol/L
- 2.0 mol/L
Correct answer: 0.2 mol/L
Moles of NaCl = 5.85/58.5 = 0.1 mol; concentration = 0.1 mol ÷ 0.5 L = 0.2 mol/L.
EmSAT Chemistry 4
What is the IUPAC name of the compound CH₃CH₂CH(OH)CH₃?