Answer:
mass of NH₃ formed when 22g of H₂ react completely = 124.67 grams
Step-by-step explanation:
3H₂ + N₂ → 2NH₃
What is stoichiometry
The ratio of coefficients of reactants and products in the above reaction equation (3 : 1 : 2), is known as the stoichiometry of the reaction.
A stoichiometric amount of a reagent is the the optimum amount or ratio where, assuming that the reaction proceeds to completion, all of the reagent is consumed, there is no deficiency of the reagent, and there is no excess of the reagent. Thus if the stoichiometry of a reaction is known, as well as the mass of one of the substances, then it is possible to calculate the mass of any of the other substances.
What is a mole?
The mole is a unit of amount of substance established by the International System of Units, to make expressing amounts of reactant or product in a reaction more convenient. As defined by Avogadro's Constant, a mole is 6.022×10²³ amounts of something. The mole is used in stoichiometric calculations, instead of the mass.
Converting between mass and moles
To convert from mass to moles, we need to divide the mass present in grams, by the molar mass of the substance (the sum of the molar masses of the individual elements comprising the compound), in g/mol, to get the moles. This can be represented by the formula: n = m/M, where n = number of moles, m = mass, M = molar mass.
So if we have 22 g of H₂ gas, which reacts completely, and therefore is a stoichiometric amount, then converting this to moles:
n(H₂) = m/M = 22/2 = 11 mol.
Using our stoichiometry, we can see that the ratio of H₂ to NH₃ = 3 : 2.
Therefore, for every 3 moles of H₂ used, we produce 2 moles of NH₃.
n(NH₃) = 2/3 × n(H₂) = 2/3 × 11 = 7.333 mol.
Finally, converting moles back to mass we get:
m(NH₃) = n×M = 7.333×17 = 124.67 grams
∴ mass of NH₃ formed when 22g of H₂ react completely = 124.67 grams