Chapter 4 Compounds and Stoichiometry Flashcards
What is a molecule?
A molecule is a combination of two or more atoms held together by a covalent bond
What is molecular weight?
the sum of atomic weights for all atoms in a molecule
What is the formula weight?
Formula weight of an ionic compound is found by adding up the atomic weights of the constituent ions according to its empirical formula.
What does the law of constant composition state?
It states that any pure sample of a given compound will contain the same elements in an identical mass ratio. For instance, every sample of water will contain 2 hydrogen atoms per every oxygen atom
Empirical formula v molecular formula
empirical formula will give the simplest whole number ratio of elements in the compound
molecular formula will give the exact number of atoms in each element in the compound and often is a multiple of the empirical formula
What is the percent composition?
percent composition = (mass of element in formula)/(molar mass) *100%
Explain composition reactions.
A combination reaction has two or more reactants forming one product. Combination reactions have more reactants than products:
A + B → C
Example: the burning of hydrogen gas in air to form water
2H2 (g) + O2 (g) → 2H2O (g)
Explain decomposition reactions.
In a decomposition reaction, a single reactant breaks down into two or more products (decomposition reactions generally have more products than reactants), usually as a result of heating, high frequency radiation, or electrolysis
A → B + C
Example: breakdown of mercury(II)oxixide
2HgO (s) → 2Hg (l) + O2 (g) (there is a delta sign over the area that signifies heat)
Explain combustion reactions.
Combustion involves oxidation (using O2 or similar) of a fuel (typically a hydrocarbon)
In its most common form, these reactants (Oxidant and a hydrocarbon) form two products: carbon dioxide and water
Example: combustion of methane
CH4 + 2O2 → CO2 + 2H2O
Explain single displacement reactions.
A single displacement reaction occurs when an atom or ion in a compound is replaced by an atom or ion in another element
Example:
Explain double displacement reactions
also called metathesis reactions
elements from two different compounds swap places with each other to form two new compounds
explain neutralization reactions.
neutralization reactions are a specific type of double-displacement reaction in which an acid reacts with a base to produce a salt (and usually water)
example:
HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)
How do you calculate percent yeild?
percent yield = (actual yield/theoretical yield) * 100%
What do ionic bonds rely on?
Ionic bonds rely on the force of electrostatic attraction between oppositely charged particles
What are electrolytes?
Electrolytes are solutes that enable solutions to carry current
