Polytechnic Chemistry 2 — Questions and Answers
Question 1: What is an exothermic reaction?
- A reaction that releases heat to the surroundings (Correct answer)
- A reaction that absorbs heat from the surroundings
- A reaction that produces light
- A reaction that requires high temperature
Correct answer: A reaction that releases heat to the surroundings
Exothermic reactions release energy (usually as heat) to the surroundings, resulting in a negative enthalpy change (ΔH < 0).
Question 2: What is the molecular formula of water?
- H₂O (Correct answer)
- HO₂
- H₂O₂
- HO
Correct answer: H₂O
Water has the molecular formula H₂O, consisting of two hydrogen atoms bonded to one oxygen atom.
Question 3: What does the periodic table organize elements by?
- Increasing atomic number (Correct answer)
- Increasing atomic mass only
- Alphabetical order
- Decreasing electronegativity
Correct answer: Increasing atomic number
Elements in the modern periodic table are arranged in order of increasing atomic number (number of protons).
Question 4: What type of reaction is: A + BC → AC + B?
- Single displacement (substitution) reaction (Correct answer)
- Double displacement reaction
- Synthesis reaction
- Decomposition reaction
Correct answer: Single displacement (substitution) reaction
In a single displacement reaction, one element replaces a similar element in a compound.
Question 5: What is a mole in chemistry?
- A unit representing 6.022 × 10²³ particles (Correct answer)
- A unit of mass equal to one gram
- A unit of concentration
- A unit of molecular weight
Correct answer: A unit representing 6.022 × 10²³ particles
A mole is a standard unit of amount in chemistry representing 6.022 × 10²³ particles (atoms, molecules, or ions).
Question 6: What is oxidation in a redox reaction?
- Loss of electrons (Correct answer)
- Gain of electrons
- Gain of protons
- Loss of protons
Correct answer: Loss of electrons
Oxidation is defined as the loss of electrons by a species in a redox reaction.
Polytechnic Chemistry 2
What is an exothermic reaction?