Question

Stoichiometry is best defined as the

Answer 1

Stoichiometry is “quantitative relationship” among the “reactants” and the “products” in a “chemical reaction”.

Explanation:  

In stoichiometry “stoicheion” means element and “metron” means measure in Greek. The stoichiometric calculation depends upon “stoichiometric coefficients” in a “chemical equation” which can be explained as the “number of moles” of each substance (reactants or products). Stoichiometric calculation is done as follows:

For example reaction between nitrogen and hydrogen to form ammonia as

$\mathrm{N}_{2}(\mathrm{g})+3 \mathrm{H}_{2}(\mathrm{g}) \longrightarrow 2 \mathrm{NH}_{3}(\mathrm{g})$

Here stoichiometric coefficients show that “one molecule of nitrogen” reacts with “three molecules of hydrogen” to form “two molecules of ammonia”. Multiplying Avogadro number $6.022 \times 10^{23}$ to no of molecules in equation:

$\text { For } \mathrm{N}_{2}: 1 \times 6.022 \times 10^{23}=1 \mathrm{mol}$

$\text { For } 3 \mathrm{H}_{2}: 3 \times 6.022 \times 10^{23}=3 \mathrm{mol}$

$\text { For } 2 \mathrm{NH}_{3}: 2 \times 6.022 \times 10^{23}=2 \mathrm{mol}$

Taking molar masses into consideration:  

$\text { For } \mathrm{N}_{2}: 1 \times 28.0=28.0 \mathrm{gm}$

$\text { For } 3 \mathrm{H}_{2}: 3 \times 2=6.0 \mathrm{gm}$

$\text { For } 2 \mathrm{NH}_{3}: 2 \times 17=34 \mathrm{gm}$

Hence balanced equation gives stoichiometric coefficients which gives proportion by moles.