IGCSE CHEMISTRY: KEY CALCULATIONS (DOUBLE).
Trusted by students across multiple disciplines!
A sample of bromine contained the two isotopes in the following proportions: bromine-
79 = 50.7% and bromine-81 = 49.3%. Calculate the relative atomic mass of bromine -
Answer: ((79x50.7)+(81x49.3))/100 = 79.99
Calculate the relative formula mass(Mr) of carbon dioxide (CO₂) - Answer: 44
What are the units for amount in Chemistry? - Answer: Moles
What is the equation linking moles, Mᵣ and mass - Answer: moles = mass / Mᵣ
What mass of carbon dioxide is produced when 24g of carbon undergoes completely
combustion? - Answer: 88g
State the expression for calculating % yield. - Answer: % yield = (actual amount of
products/theoretical amount of products) x 100
State the steps for calculating empirical formula - Answer: 1) mass/Aᵣ. 2) divide by the
smallest. 3) Give the ratio has a whole number. 4) State final empirial formula
What is meant by the term empirical formula? - Answer: A chemical formula that shows
the simplest ratio of the numbers of atoms in a compound
What is meant by the term molecular formula? - Answer: A chemical formula that shows
the actual numbers of the different types of atoms in a molecule
An oxide of nitrogen contains 26% nitrogen and 74% oxygen and has a relative
molecular mass of 108. Find the empirical and molecular formulae for the oxide. -
Answer: Empirical formula is N₂O₅. Molecular formula is also N₂O₅
1
APPHIA - Crafted with Care and Precision for Academic Excellence.
Trusted by students across multiple disciplines!
A sample of bromine contained the two isotopes in the following proportions: bromine-
79 = 50.7% and bromine-81 = 49.3%. Calculate the relative atomic mass of bromine -
Answer: ((79x50.7)+(81x49.3))/100 = 79.99
Calculate the relative formula mass(Mr) of carbon dioxide (CO₂) - Answer: 44
What are the units for amount in Chemistry? - Answer: Moles
What is the equation linking moles, Mᵣ and mass - Answer: moles = mass / Mᵣ
What mass of carbon dioxide is produced when 24g of carbon undergoes completely
combustion? - Answer: 88g
State the expression for calculating % yield. - Answer: % yield = (actual amount of
products/theoretical amount of products) x 100
State the steps for calculating empirical formula - Answer: 1) mass/Aᵣ. 2) divide by the
smallest. 3) Give the ratio has a whole number. 4) State final empirial formula
What is meant by the term empirical formula? - Answer: A chemical formula that shows
the simplest ratio of the numbers of atoms in a compound
What is meant by the term molecular formula? - Answer: A chemical formula that shows
the actual numbers of the different types of atoms in a molecule
An oxide of nitrogen contains 26% nitrogen and 74% oxygen and has a relative
molecular mass of 108. Find the empirical and molecular formulae for the oxide. -
Answer: Empirical formula is N₂O₅. Molecular formula is also N₂O₅
1
APPHIA - Crafted with Care and Precision for Academic Excellence.
