Chemistry calculations might seem intimidating, but they're actually just clever...
Chemistry248 views·Updated 29 Aug 2026·2 pagesEssential Quantitative Chemistry Notes and Quick Questions
A
Ali @ali_wnmq
1
of 2
Chemical Measurements and Conservation of Mass
Ever wonder why your chemistry teacher insists that "atoms can't just disappear"? Conservation of mass is the golden rule - during any chemical reaction, the total mass of reactants always equals the total mass of products. No atoms are lost or created, they just get rearranged.
Relative formula mass (Mr) is simply adding up all the atomic masses in a compound's formula. For water (H₂O), that's 1+1+16 = 18. This number becomes crucial when you're working out how much product you'll get from your reactants.
Sometimes it looks like mass changes during reactions - usually because one of your reactants or products is a gas that escapes or gets absorbed from the air. The mass is still conserved; you just can't see where it's gone!
Key insight: In balanced equations like 2Mg + O₂ → 2MgO, the numbers tell you exactly how many moles react together - master this and you'll never struggle with chemical calculations again.
Limiting reactants determine how much product you can actually make. Just like making sandwiches, if you run out of bread first, that's your limiting factor - even if you have loads of cheese left over.
2
of 2
Advanced Calculations: Yield, Atom Economy and Solutions
Real chemistry isn't perfect - you'll never get 100% of your expected product. Percentage yield compares what you actually made to the theoretical maximum, and it's calculated as: (actual mass ÷ theoretical mass) × 100.
Atom economy measures how much of your starting materials end up as useful products rather than waste. High atom economy is brilliant for the environment and your wallet - nobody wants to throw away expensive reactants!
Concentration tells you how much stuff is dissolved in a solution. You can measure it in g/dm³ (grams per litre) or mol/dm³ (moles per litre). Higher concentration means more particles crammed into the same space.
Pro tip: For gas calculations, remember that one mole of any gas takes up 24 dm³ at room temperature and pressure - this makes volume calculations surprisingly straightforward.
Titrations are like chemical detective work - you use one solution with a known concentration to work out the concentration of another. The balanced equation tells you exactly how the chemicals react together, so you can calculate backwards from your results.
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Chemistry248 views·Updated 29 Aug 2026·2 pagesEssential Quantitative Chemistry Notes and Quick Questions
A
Ali @ali_wnmq
Chemistry calculations might seem intimidating, but they're actually just clever ways of measuring and tracking atoms during reactions. Once you understand the basic principles of conservation of mass and moles, you'll be able to predict exactly what happens in any...
1
of 2
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Chemical Measurements and Conservation of Mass
Ever wonder why your chemistry teacher insists that "atoms can't just disappear"? Conservation of mass is the golden rule - during any chemical reaction, the total mass of reactants always equals the total mass of products. No atoms are lost or created, they just get rearranged.
Relative formula mass (Mr) is simply adding up all the atomic masses in a compound's formula. For water (H₂O), that's 1+1+16 = 18. This number becomes crucial when you're working out how much product you'll get from your reactants.
Sometimes it looks like mass changes during reactions - usually because one of your reactants or products is a gas that escapes or gets absorbed from the air. The mass is still conserved; you just can't see where it's gone!
Key insight: In balanced equations like 2Mg + O₂ → 2MgO, the numbers tell you exactly how many moles react together - master this and you'll never struggle with chemical calculations again.
Limiting reactants determine how much product you can actually make. Just like making sandwiches, if you run out of bread first, that's your limiting factor - even if you have loads of cheese left over.
2
of 2Sign up to see the content. It's free!
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Advanced Calculations: Yield, Atom Economy and Solutions
Real chemistry isn't perfect - you'll never get 100% of your expected product. Percentage yield compares what you actually made to the theoretical maximum, and it's calculated as: (actual mass ÷ theoretical mass) × 100.
Atom economy measures how much of your starting materials end up as useful products rather than waste. High atom economy is brilliant for the environment and your wallet - nobody wants to throw away expensive reactants!
Concentration tells you how much stuff is dissolved in a solution. You can measure it in g/dm³ (grams per litre) or mol/dm³ (moles per litre). Higher concentration means more particles crammed into the same space.
Pro tip: For gas calculations, remember that one mole of any gas takes up 24 dm³ at room temperature and pressure - this makes volume calculations surprisingly straightforward.
Titrations are like chemical detective work - you use one solution with a known concentration to work out the concentration of another. The balanced equation tells you exactly how the chemicals react together, so you can calculate backwards from your results.
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