Chemical quantities

Chemical quantities are where chemistry meets arithmetic, and small setup mistakes cost the most marks. This topic covers the two calculations that everything else builds on. First is converting grams to moles using molar mass. The common slip is multiplying by the molar mass when you should divide, so the page shows how to let units guide the direction: grams divided by grams per mole leaves moles. Second is molarity, moles of solute per litre of solution. Here students often forget to convert millilitres to litres, which makes an answer a thousand times too big or too small. Both pages lean on rearranging a simple formula, so if dividing both sides still feels shaky, review that algebra page first. Always write units at every step, and cancel them as you go. When the units left at the end match what the question asked for, your setup is almost certainly right, and you can trust the number that comes out of the calculator.