The Basics of Chemical Calculations
Ever wondered why chemists are obsessed with balancing equations? It all comes down to the law of conservation of mass - atoms can't just disappear or magically appear during reactions. The total mass going in equals the total mass coming out, which is why balanced equations are absolutely essential.
Relative formula mass (Mr) is your best mate for chemical calculations. Simply add up all the relative atomic masses of every atom in a compound's formula. It's like counting the total "weight" of all the ingredients in a chemical recipe.
When you see reactions happening in test tubes or flasks with stoppers, you're looking at closed systems where nothing can escape. But in open systems, gases can float away or enter from the air, making it look like mass has been lost or gained - though it never actually has!
Top Tip: Mass changes are often just gases you can't see entering or leaving the reaction!
Percentage composition tells you exactly how much of each element makes up a compound. Calculate it by dividing an element's mass by the total compound mass, then multiply by 100. All percentages in a compound will always add up to 100%.
