Ch 4 - Compounds and Stoichiometry Flashcards
What are compounds?
substances composed of 2+ elements in a fixed proportion
What is the difference between molecular weight and molecular mass?
- weight: the mass (in amu) of the constituent atoms in a compound as indicated by the molecular formula
- mass: mass of one mle (Avagadro’s number) of a compound; usually measured in grams per mole
What gram equivalent weight?
a measure of the mass of a substance that can donate one equivalent of the species of interest
What is normality?
the ratio of equivalent per liter; it is related to molarity by multiplying the molarity by the number of equivalents present per mole of the compound
What are equivalents?
moles of the species of interest; most often seen in acid-base chemistry and redox reactions
What is the law of constant composition?
any pure sample of a compound will contain the same elements in the same mass ratio
What is the difference between the empirical formula and the molecular formula?
- empirical: smallest whole number ratio of the elements in the compound
- molecular: either the same as or a multiple of the empirical formula; it gives the exact number of atoms of each element in a compound
How do you calculate the percent composition by mass?
determine the mass of the individual element and divide by the molar mass of the compound
When do combination reactions occur?
when 2+ reactants combine to form one product
When do decomposition reactions occur?
when one reactant is chemically broken down into 2+ products
When do combustion reactions occur?
when a fuel and an oxidant (typically oxygen) react, foring the products water and carbon dioxide
When do displacement reactions occur?
when 1+ atoms or ions of one compound are replaced with one or more atoms or ions of another compound
What is the difference between single- and double-displacement reactions?
- single: occur when elements from 1 compound is replaced with another element
- double: occur when elements from 2 different compounds trade places with each other to form 2 new compounds
What are neutralization reactions?
an acid reacts with a base to form a salt (and usually water)
What is the difference between limiting and excess reagents?
- limiting: reactant that will be consumed first in a chemical reaction
- excess: other reactant
