Chemistery

Stoichiometry sounds like the hardest word in the chapter and turns out to be the most mechanical part of it. It's a recipe calculation: if this much goes in, how much comes out? Once you learn one route through it, every problem uses the same route. The short answer: stoichiometry is using the coefficients of a balanced chemical equation as a mole ratio to work out how much of one substance reacts with, or is produced by, another. The coefficients compare moles , never grams — which is why every problem passes through moles on the way. What the coefficients actually tell you Take the reaction that makes ammonia: N₂ + 3 H₂ → 2 NH₃ Read it as a ratio: 1 mole of N₂ reacts with 3 moles of H₂ to make 2 moles of NH₃. That's the mole ratio, and it comes free with a balanced equation. What it does not say is that 1 gram of N₂ reacts with 3 grams of H₂. Different substances have different molar masses, so grams don't scale that way. Coefficients count particles, not we...

A chemical equation looks like a secret code: letters, numbers, little subscripts, an arrow. But it's actually a precise recipe that tells you exactly what goes in, what comes out, and in what proportions. Learn to read and balance one and you can describe any reaction on a single line. The short answer: a chemical equation is a shorthand way of writing a chemical reaction using formulas instead of words, with reactants on the left, products on the right, and an arrow between them. A balanced equation has the same number of each type of atom on both sides , because atoms are never created or destroyed — only rearranged. How to read the symbols Take the equation for burning methane: CH₄ + 2 O₂ → CO₂ + 2 H₂O Formulas (CH₄, O₂) name the substances. Small subscripts tell you how many atoms are in one molecule — the "4" in CH₄ means four hydrogens. Coefficients are the big numbers in front (the "2" in 2 O₂). They tell you how many of that whole molecule...

Every chemical equation is really a tiny before-and-after story. The trouble is that "before" and "after" have intimidating names — reactants and products — and it's easy to mix up which is which. Here's the simple rule that makes it stick. The short answer: reactants are the starting substances you begin a reaction with — they sit on the left of the arrow. Products are the new substances the reaction makes — they sit on the right of the arrow. The arrow (→) always points from reactants to products, meaning "turns into." Quick comparison at a glance Feature Reactants Products What they are Starting substances Substances formed Side of the arrow Left Right When they exist Before the reaction After the reaction During the reaction Used up (consumed) Built up (created) Arrow direction Arrow points away from them Arrow points toward them Example (burning carbon) C and O₂ CO₂ The whole idea lives in tha...