Chemical calculations are essential skills that help you work out...
Chemistry115 views·Updated 29 Aug 2026·2 pagesNat5 Chemistry - Mastering Calculations
Olivia Churcher@oliviachurcher
1
of 2
Basic Chemical Calculations
Working out formula mass is your starting point for most chemistry calculations. You'll need to add up the mass of every single atom in a chemical formula - sounds tricky, but it's just careful addition once you know the steps.
Start by writing down the formula (usually given in exam questions), then count how many atoms of each element you've got. Use your data booklet to find the relative atomic mass (RAM) for each element, then multiply and add everything together.
Percentage composition tells you what fraction of a compound is made up of one particular element. Calculate the total mass first, work out how much mass comes from your specific element, then convert to a percentage using the formula: % by mass = (mass of element ÷ total mass) × 100.
Quick Tip: Always double-check your atom counting - it's the most common mistake that trips students up in formula mass calculations.
2
of 2
Moles and Concentration
Moles are chemistry's way of counting particles, and they're connected to mass through the gram formula mass (GFM). Think of moles as a bridge between the tiny atomic world and the masses you can actually measure in the lab.
The key relationship you need to master is: moles = mass ÷ GFM. This triangle relationship means you can rearrange to find any of these three values if you know the other two.
Concentration measures how much substance is dissolved in a given volume of solution. It's usually measured in mol/L and connects moles, concentration, and volume together in another essential relationship.
Remember: These formulas work like puzzle pieces - once you identify what you're given and what you need to find, the calculation method becomes clear.
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Chemistry115 views·Updated 29 Aug 2026·2 pagesNat5 Chemistry - Mastering Calculations
Olivia Churcher@oliviachurcher
Chemical calculations are essential skills that help you work out exactly how much of each substance you're dealing with in reactions. These fundamental maths tools will help you ace your chemistry exams and understand what's actually happening in chemical processes.
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Basic Chemical Calculations
Working out formula mass is your starting point for most chemistry calculations. You'll need to add up the mass of every single atom in a chemical formula - sounds tricky, but it's just careful addition once you know the steps.
Start by writing down the formula (usually given in exam questions), then count how many atoms of each element you've got. Use your data booklet to find the relative atomic mass (RAM) for each element, then multiply and add everything together.
Percentage composition tells you what fraction of a compound is made up of one particular element. Calculate the total mass first, work out how much mass comes from your specific element, then convert to a percentage using the formula: % by mass = (mass of element ÷ total mass) × 100.
Quick Tip: Always double-check your atom counting - it's the most common mistake that trips students up in formula mass calculations.
2
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Moles and Concentration
Moles are chemistry's way of counting particles, and they're connected to mass through the gram formula mass (GFM). Think of moles as a bridge between the tiny atomic world and the masses you can actually measure in the lab.
The key relationship you need to master is: moles = mass ÷ GFM. This triangle relationship means you can rearrange to find any of these three values if you know the other two.
Concentration measures how much substance is dissolved in a given volume of solution. It's usually measured in mol/L and connects moles, concentration, and volume together in another essential relationship.
Remember: These formulas work like puzzle pieces - once you identify what you're given and what you need to find, the calculation method becomes clear.
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