Empirical and molecular formulaeAQA A-Level Chemistry: Flashcards
What these 12 flashcards ask
- Define empirical formula.
- Define molecular formula.
- What is the empirical formula of glucose, C₆H₁₂O₆?
- Which compounds have the same empirical and molecular formula?
- First step in finding an empirical formula from percentages?
- After dividing amounts by the smallest, what if you get 1 : 1.5?
- What multiplier turns 1 : 1.33 into whole numbers?
- What multiplier turns 1 : 1.25 into whole numbers?
- How do you find the molecular formula from the empirical formula?
- A compound has empirical formula CH₂ and Mr = 56.0. Molecular formula?
- How do you find the mass of oxygen in an oxide when it is not given?
- Why must empirical formulae use whole numbers?
Exam questions on Empirical and molecular formulae
- Chemists in a food laboratory identify sugars and acids from their formulae. They record that glucose has the molecular formula C₆H₁₂O₆.State the empirical formula of glucose and explain how it differs from its molecular formula.2 marks
- An organic compound X contains only carbon and hydrogen. Analysis shows it contains 85.7% carbon and 14.3% hydrogen by mass, and its relative molecular mass is 56.0. Use Ar values: C = 12.0, H = 1.0.Calculate the molecular formula of compound X.2 marks
- A 2.00 g sample of an iron oxide is heated in a stream of hydrogen until it is completely reduced to iron. The mass of iron produced is 1.40 g. Use Ar values: Fe = 55.8, O = 16.0.Calculate the amount, in mol, of iron and the amount, in mol, of oxygen in the sample.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).