Stoichiometry is the study of the quantitative relationships, based on mole ratios, between the reactants and products in a chemical reaction.
Stoichiometry is the study of the quantitative relationships, based on mole ratios, between the reactants and products in a chemical reaction. Malay: stoikiometri · Chinese: 化学计量.
In practice, stoichiometry lets you predict how much product a reaction will make, or how much reactant you need, using the balanced equation. The general method is to convert a given mass or volume into moles, apply the mole ratio from the equation to find the moles of the substance you want, and then convert that back into a mass, a volume of gas or a number of particles.
Example. Suppose two moles of hydrogen react completely with oxygen in 2H2 + O2 → 2H2O. The mole ratio of hydrogen to water is 2:2, so two moles of hydrogen give two moles of water. Since the molar mass of water is 18 g mol−1, that is 2 × 18 = 36 g of water. The same three-step approach, from a measured quantity to moles, then across the mole ratio, then back out again, works for any reaction once the equation is balanced.
Confusion to avoid. Stoichiometry always starts from a balanced equation, so a common mistake is to use unbalanced coefficients and get the ratio wrong. Remember also that you must work in moles, not in grams, when applying the ratio, converting to and from mass only at the beginning and end of the calculation. Comparing masses directly through the coefficients is a mistake, because equal coefficients do not mean equal masses.
In this chapter stoichiometry is the destination that all the other terms lead to: the mole, molar mass, molar volume, the balanced equation and the mole ratio all come together here, which is why it is the climax of the mole concept in SPM Chemistry.
Want a teacher to make this click?
We teach SPM Chemistry one to one, so your child understands it and scores it.
from RM50/hr · One-hour paid trial · Same-day reply