Question 1
Which of the following best defines a base according to the Brønsted-Lowry model?No clue? Show me the answer
Correct answerCorrect!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Recall the Brønsted-Lowry model
The Brønsted-Lowry model was developed in 1923 and describes acids and bases in terms of proton transfer.
Step 2: Define a base
In the Brønsted-Lowry model, a BASE is a proton (H⁺) ACCEPTOR.
Step 3: Distinguish from Arrhenius definition
Producing OH⁻ ions is the older Arrhenius definition. The Brønsted-Lowry definition is broader — it explains why NH₃ is a base even though it contains no OH⁻.
Step 4: Select the correct answer
The correct answer is: 'A substance that accepts protons (H⁺ ions).'
Method #2Process of EliminationStep 1: Eliminate pH < 7
DA substance with a pH less than 7'A substance with a pH less than 7' describes an ACID, not a base. Eliminate this option.
Step 2: Eliminate proton donor
CA substance that donates protons (H⁺ ions)'A substance that donates protons (H⁺ ions)' is the Brønsted-Lowry definition of an ACID. Eliminate this option.
Step 3: Evaluate the OH⁻ option
Producing OH⁻ is a property of bases (Arrhenius definition), but the question specifically asks about the Brønsted-Lowry model, which defines bases as proton acceptors — a broader definition.
Step 4: Confirm the answer
The only option matching the Brønsted-Lowry model is 'A substance that accepts protons (H⁺ ions).'
Question 2
What is the key difference between a base and an alkali?No clue? Show me the answer
Correct answerCorrect!IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Direct ApproachStep 1: Define both terms
A base accepts protons (H⁺). An alkali is a specific type of base that dissolves in water and produces OH⁻ ions in solution.
Step 2: Establish the relationship
All alkalis are bases, but not all bases are alkalis. For example, copper oxide (CuO) is a base but does not dissolve in water, so it is not an alkali.
Step 3: Identify the correct answer
The correct answer is: 'An alkali is a base that dissolves in water to produce OH⁻ ions.'
Method #2Process of EliminationStep 1: Eliminate the reversed relationship
DAll bases are alkalis, but not all alkalis are bases'All bases are alkalis, but not all alkalis are bases' reverses the correct relationship. This is wrong — eliminate it.
Step 2: Eliminate the false pH claim
AAlkalis have a higher pH than basesThe statement that 'alkalis have a higher pH than bases' is not a defining difference — both are bases with pH > 7. Eliminate this option.
Step 3: Eliminate the hydroxide claim
Bases do NOT always contain hydroxide ions — ammonia (NH₃) is a base with no OH⁻ group. Eliminate this option.
Step 4: Confirm the correct answer
The remaining option — 'An alkali is a base that dissolves in water to produce OH⁻ ions' — correctly describes the relationship.
13 more questions in this topic
Pick this up in your Library: it holds the whole topic, notes, cheatsheet and questions. Your answers here are kept on this device.