OCR A-Level Chemistry AS Breadth in chemistry (01), November 2020: Question 2
1 mark · Easy difficulty · Multiple Choice
Identify the correct chemical formula for silver carbonate from the given multiple-choice options.
Practise this questionQuestion
Question text
2 What is the formula of silver carbonate?
A AgCO3
B Ag(CO3)2
C Ag2CO3
D Ag3CO3
Your answer [1]
Mark scheme
Show the mark scheme
2 C 1 1.2
How to answer it
Determining Ionic Formulae: Silver Carbonate
What this question tests
This question assesses your fundamental chemical knowledge of ion charges (oxidation states/valencies) and your ability to construct correct chemical formulae for ionic compounds by balancing positive and negative charges to achieve overall electrical neutrality.
What is the formula of silver carbonate?
✅ Correct Answer
C: Ag₂CO₃
💡 Key Knowledge
- Transition metal silver (Ag) forms a stable ion with a fixed charge: Ag⁺ .
- Carbonate is a common polyatomic ion with a formula of CO₃²⁻ .
- To achieve a neutral compound, the total positive charge must equal the total negative charge.
🧠 Exam Technique
- The "Swap and Drop" Method: Take the numerical value of the charge on one ion and use it as the subscript for the other.
- Ag⁺ (charge 1) and CO₃²⁻ (charge 2) gives Ag₂ and (CO₃)₁ , simplifying to Ag₂CO₃ .
❌ Common Errors
- Assuming silver has a variable charge like other transition metals (e.g., iron). Silver almost exclusively forms Ag⁺ in AS-level chemistry.
- Failing to balance the 2- charge of the carbonate ion, leading to incorrect formulae like option A ( AgCO₃ ).
- Forgetting that transition metals usually form positive ions and writing them the wrong way around.
Topics
Module 2: Foundations in chemistry · 2.1 Atoms and reactions
Question and mark scheme from the OCR A-Level Chemistry examination, AS Breadth in chemistry (01), November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.