Stoichiometry Formula: Stoichiometry, a term derived from the Greek words “stoicheion,” meaning elementary constituent, and “metrin,” referring to measuring, involves quantitative calculations concerning the reactants and products in chemical reactions. It is grounded in the principle of the conservation of mass, where the combined mass of reactants equals the combined mass of the products. Stoichiometry allows for the precise determination of product quantities when the quantities of the individual reactants are known.
For instance, in the chemical equation:
CH4 + 2 O2 → CO2 + 2 H2O
Here, one molecule of methane (CH4) reacts with two molecules of oxygen gas to yield two molecules of carbon dioxide (CO2) and two molecules of water (H2O). Stoichiometry quantifies this relationship and is employed to ascertain the quantities of reactants produced in a given reaction.
Also Check – Theoretical Yield Formula
What Is Stoichiometry?
In simpler terms, we can define stoichiometry as the calculation of the quantities of products and reactants involved in a chemical reaction, primarily focusing on numerical values.
Stoichiometry is a vital concept in Chemistry, enabling us to use balanced chemical equations to compute the quantities of reactants and products involved. This involves the application of ratios from the balanced equation. Essentially, all reactions depend on a fundamental factor the quantity of substance present.
Also Check – Degree Of Unsaturation Formula
Stoichiometry Formula Solved Examples
Example 1: Ammonia reacts with solid copper oxide, resulting in the release of nitrogen gas, solid copper, and water vapor. Write the chemical reaction and balance the equation according to stoichiometry.
Solution: The chemical reaction can be expressed as:
NH3 + CuO → Cu + H2O + N2
The balanced equation, considering stoichiometry, is:
2 NH3 + 3 CuO → 3 Cu + 3 H2O + N2
Example 2: Sulfur trioxide gas is generated when iron pyrites (FeS2) undergoes combustion. Please outline the chemical reaction and balance the equation by considering the stoichiometry of each compound.
Solution: The chemical reaction for this example is:
FeS2 + O2 → Fe2O3 + SO3
Combustion compounds react with oxygen.
The balanced chemical equation, taking stoichiometry into account, is:
4 FeS2 + 15 O2 → 2 Fe2O3 + 8 SO3
Also Check – Dilution Formula
Example 3: Combustion of Hydrogen Gas
When hydrogen gas (H2) combusts in the presence of oxygen gas (O2), it forms water vapor (H2O). Let’s write the chemical reaction and balance the equation using stoichiometry.
H2 + O2 → H2O
In this scenario, a single molecule of hydrogen (H2) reacts with one molecule of oxygen (O2) to yield one molecule of water (H2O). To achieve a balanced equation using stoichiometry, it’s essential to maintain an equal count of each type of atom on both sides. Since hydrogen is present twice in the reactants, we balance it by introducing a coefficient of 2 in front of H2O:
2 H2 + O2 → 2 H2O
This balanced equation represents the stoichiometric proportions in the reaction, allowing us to calculate the quantities of reactants and products accurately.
Also Check – Gas Pressure Formula
Example 4: Formation of Sodium Chloride (Table Salt)
When sodium metal (Na) reacts with chlorine gas (Cl2), sodium chloride (NaCl), commonly known as table salt, is formed. Let’s write the chemical reaction and balance it using stoichiometry.
Na + Cl2 → NaCl
In this reaction, one sodium atom (Na) reacts with one chlorine molecule (Cl2) to produce one molecule of sodium chloride (NaCl). The equation is already balanced, as the number of each type of atom is the same on both sides.
Example 5: Formation of Calcium Oxide
Calcium metal (Ca) reacts with oxygen gas (O2) to produce calcium oxide (CaO), commonly known as quicklime. Let’s write the chemical reaction and balance it using stoichiometry.
Ca + O2 → CaO
In this particular reaction, a single calcium atom (Ca) undergoes a reaction with a single molecule of oxygen (O2) to yield a solitary molecule of calcium oxide (CaO). Notably, the equation is inherently balanced, with an equal count of each type of atom on both sides.
In each of these examples, stoichiometry enables us to determine the precise quantities of reactants needed and products formed in chemical reactions by applying the principles of balanced equations. It is a fundamental concept in chemistry, providing valuable insights into the quantitative aspects of chemical transformations.
Stoichiometry Formula FAQs
What is stoichiometry?
Stoichiometry constitutes a subfield within chemistry dedicated to examining the quantitative connections between the starting materials (reactants) and resulting substances (products) involved in chemical reactions.
Why is stoichiometry important?
Stoichiometry is crucial because it allows us to predict and calculate the amounts of reactants needed and products formed in chemical reactions, enabling precise control in laboratories and industrial processes.
What is a stoichiometric coefficient?
A stoichiometric coefficient is an integer placed at the beginning of a chemical formula within a balanced chemical equation, serving to guarantee that the equation adheres to the principle of conserving mass.
What is the mole ratio in stoichiometry?
The mole ratio represents the relationship between the number of moles of one substance in a chemical reaction to the number of moles of another substance. It is derived from the balanced chemical equation.