Key Concepts in Stoichiometry and Chemical Reactions

What is a conversion factor and why is it useful?

A conversion factor is a numerical ratio or fraction used to express a measurement where the units change but the value remains the same. It is useful for finding different measurements of a substance without altering its value.

How can you describe 'the mole' using an analogy?

The mole is the amount of substance that contains 6.022x10^23 of anything, similar to how a dozen refers to twelve of something. One mole of an element indicates there are 6.022x10^23 atoms of that element.

How are relative atomic mass and molar mass related?

Relative atomic mass is the weight of an element in atomic mass units (amu) as found on the periodic table, while molar mass is the molecular/formula mass in grams per mole (g/mol). They are equivalent; the molar mass of an element equals its relative atomic mass.

What are the symbols and units for mass, molar mass, and moles?

Mass: m (u), Molar mass: M (g/mol), Moles: n (mol).

What is the link between amount of substance and moles?

The link is the conversion factor of 6.022x10^23 over 1 mol or vice versa.

What is the Law of Definite Proportions?

Different samples of the same compound always contain the same proportions by mass of its constituent elements.

What is the difference between empirical and molecular formulas?

The empirical formula shows the simplest whole-number ratio of atoms/ions in a compound, while the molecular formula provides the actual number of atoms of each element in one molecule. The molecular formula is more useful to scientists.

Define stoichiometry.

Stoichiometry is the study of the quantitative aspects of chemical reactions.

What is critical before starting any stoichiometry problem?

It is critical that the chemical equation is balanced to ensure the law of conservation is upheld and the mole ratio remains consistent.

How do you compare limiting and excess reagents using an analogy?

A limiting reagent is like the ingredient that runs out first in a recipe, preventing further production (e.g., cheese for burgers), while excess reagents are the leftover ingredients after the reaction is complete.

What is the difference between theoretical and actual yield in a chemical reaction?

Theoretical yield is the estimated mass of product calculated from stoichiometric math under ideal conditions, while actual yield is the mass obtained from the lab experiment.

What are some reasons that percent yield may be more or less than 100%?

1) Nature of the reaction may allow products to revert to reactants. 2) Material loss during transfer or purification. 3) Impurities in chemicals. 4) Competing side reactions may produce alternative products.

Why is determining the yield of a chemical reaction important in the chemical industry?

Determining yield is crucial for process effectiveness, product quality, safety, and economic viability, providing information for cost reduction, process optimization, and sustainable production.