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iGCSE Chemistry: Key Calculations (Double)
Terms in this set (13)
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
((79x50.7)+(81x49.3))/100 = 79.99
Calculate the relative formula mass(Mr) of carbon dioxide (CO₂)
What are the units for amount in Chemistry?
What is the equation linking moles, Mᵣ and mass
moles = mass / Mᵣ
What mass of carbon dioxide is produced when 24g of carbon undergoes completely combustion?
State the expression for calculating % yield.
% yield = (actual amount of products/theoretical amount of products) x 100
State the steps for calculating empirical formula
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?
A chemical formula that shows the simplest ratio of the numbers of atoms in a compound
What is meant by the term molecular formula?
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.
Empirical formula is N₂O₅. Molecular formula is also N₂O₅
To determine the formula of a metal oxide by combustion, magnesium is heated in a crucible. Why is the crucible is cooled, weighed, reheated, cooled, re-weighed, and so on?
To make sure a constant mass has been reached and there is no more magnesium left to react
Use Q=mcΔT and c=4.18J/°C/g. 25cm³ of sulfuric acid is put into a boiling tube. The starting temperature is 21°C. A spatula of iron filings is added. After a while the temperature reaches 33°C. What is the total heat energy change?
State the units of molar enthalpy change.
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iGCSE Chemistry: Electrolysis
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