Stoikiometri

Chemists use the following formula to measure their efficiency:

Think back to our bicycle analogy. To make one bicycle, you need 1 frame and 2 wheels. If you have 5 frames but only 8 wheels, you can only make 4 bicycles. The wheels are the limiting reactant (you run out of wheels), and you will have 1 frame left over (the excess reactant).

One mole is an enormous number: 6.022 x 10²³ particles (Avogadro's number). Think of the mole as the chemist’s “dozen.” Just as a dozen always means 12 items, a mole always means 6.022 x 10²³ items. stoikiometri

2H₂ + O₂ → 2H₂O

The molar mass of H₂O = (2 × 1.01) + 16.00 = 18.02 g/mol. Moles of H₂O = (36 g) / (18.02 g/mol) ≈ 2.00 moles. Chemists use the following formula to measure their

Using the periodic table, we can convert between grams (what you can weigh on a scale) and moles (the number of particles). This is the first step in most stoichiometry problems. Let’s walk through a classic problem. Suppose you have 36 grams of water (H₂O). How many grams of hydrogen gas (H₂) are needed to make that water, assuming you have unlimited oxygen?

The molar mass of H₂ = 2 × 1.01 = 2.02 g/mol. Grams of H₂ = 2.00 moles × 2.02 g/mol = 4.04 grams. The wheels are the limiting reactant (you run

Imagine you are baking a cake. You know that to make one cake, you need 2 cups of flour, 1 cup of sugar, and 3 eggs. If you want to make three cakes, you simply multiply every ingredient by three. Chemistry works in a very similar way, but instead of cakes, we are making molecules. This mathematical “recipe book” of chemistry is called stoichiometry (pronounced stoy-kee-ah-muh-tree ).

Look at the coefficients: For every 2 moles of H₂O produced, you need 2 moles of H₂. The ratio of H₂ to H₂O is 2:2, which simplifies to 1:1. Moles of H₂ needed = 2.00 moles H₂O × (2 mol H₂ / 2 mol H₂O) = 2.00 moles H₂.

The word comes from the Greek words stoicheion (element) and metron (to measure). Simply put, The Foundation: The Balanced Equation You cannot do stoichiometry without a balanced chemical equation. A balanced equation is like a legally binding contract for atoms—it states that matter is neither created nor destroyed. The number of atoms of each element on the left side (reactants) must equal the number on the right side (products).

The other reactants are called excess reactants .