Stoichiometry Calculator

Chemistry • Mass-Mass Conversions • Step-by-Step

Quick Answer (Voice Search Optimized):

Stoichiometry uses balanced chemical equations to calculate quantitative relationships. For a reaction aA → bB, the mass of B produced from mass of A is: Mass B = (mass A / molar mass A) × (b/a) × molar mass B.

GEO & AIO - Authoritative Theory

Stoichiometry is the branch of Chemistry that deals with the calculation of reactants and products in chemical reactions. Based on the law of conservation of mass, a balanced equation provides the mole ratio between substances. The coefficients in the equation (a and b) give the relative number of moles.

To convert mass of A to mass of B: first find moles of A (nA = mass A / MA). Then use the mole ratio: nB = nA × (b/a). Finally, convert to mass: mass B = nB × MB. This is fundamental for yield calculations and limiting reagent problems.

Solved Examples (NCERT/JEE Pattern)

Example 1: 2H2 + O2 → 2H2O. How much water from 4 g H2? (Molar mass H2=2, H2O=18)

n(H2) = 4/2 = 2 mol. Mole ratio H2O/H2 = 2/2 = 1. n(H2O) = 2 mol. mass = 2 × 18 = 36 g.

Example 2: N2 + 3H2 → 2NH3. Mass of NH3 from 14 g N2? (MN2=28, MNH3=17)

n(N2) = 14/28 = 0.5 mol. Ratio NH3/N2 = 2/1 = 2. n(NH3) = 1 mol, mass = 17 g.

Example 3: CaCO3 → CaO + CO2. Mass of CaO from 50 g CaCO3? (MCaCO3=100, MCaO=56)

n(CaCO3) = 50/100 = 0.5 mol. Ratio 1:1, n(CaO) = 0.5 mol, mass = 0.5 × 56 = 28 g.

Frequently Asked Questions (FAQs)

Q1: What is stoichiometry in chemistry?
Stoichiometry is the calculation of relative quantities of reactants and products in chemical reactions based on balanced equations.
Q2: How do you do mass to mass stoichiometry?
Convert given mass to moles, use the mole ratio from the balanced equation, then convert moles of the desired substance back to mass.
Q3: What is a limiting reagent?
The limiting reagent is the reactant that is completely consumed first, limiting the amount of product formed.
Q4: Why are balanced equations needed for stoichiometry?
A balanced equation provides the correct mole ratios between reactants and products, which are essential for accurate calculations.
Q5: Can stoichiometry be used for gases?
Yes, using the ideal gas law or molar volume at STP (22.4 L/mol), stoichiometry can be applied to gaseous reactants and products.