11.1 - Describing Chemical Reactions
reactants yield products
l - liquid
g - gas
q - aqueous solution (dissolves in water)
s - solid
word equations - write names of the reactants on the left and the products on the right
hydrogen + sulfur → hydrogen sulfide
H(sub. 2) + S → H(sub. 2)S
chemical equation (aka skeletal) - shorthand method that represents a chemical reaction by using formulas of the reactants on the left and the products on the right
a catalyst can be added to a reaction
catalyst - any substance that speeds up a chemical reaction but not used up in the reactants — usually written above arrow
SYMBOLS
a plus sign separates 2 reactants/products
an arrow means “yields”
a back and forth arrow means that the reaction is reversible
a triangle over an arrow means that heat is supplied to the reaction
an element over an arrow means that the element is used as a catalyst
to balance an equation, change the coefficient, NOT the subscripts
coefficients - small whole numbers placed in front of the formula to balance the equation
balanced equation - must contain same number of atoms and elements in the reactants as the products
Zn + HCl → ZnCl + H(sub. 2)
2Zn + 2HCl → 2ZnCl + H(sub. 2)
to write a balanced equation
write skeleton equation
use coefficients
11.2 - Types of Chemical Reactions
synthesis
A + B → AB
chem chg in which 2 or more substances react to form a single new substance
decomposition
AB → A + B
chem chg in which a single compound breaks down into 2 or more simpler products
single-replacement
AB + C → A + CB
chem chg in which 1 element replaces a 2nd element in a compound
whether one metal will displace another from a compound depends upon relative reactivities of the 2 metals
activity series - lists metals in order of decreasing reactivity
reactivity of halogens decrease as you go down 7A — a halogen can replace a halogen
double-replacement
AB + CD → CB + AD
chem chg involving an exchange of positive ions between 2 compounds
combustion
chem chg in which an element or a compound reacts with oxygen, often producing energy in the form of heat and light
a compound of carbon/hydrogen and oxygen are usually the reactants
CO2 and H2O are usually the products
the number of elements and/or compounds reacting is a good indicator of possible reaction type and thus possible products
note fig. 11.10 pg 338-339
11.3 - Reactions in Aqueous Solutions
dissociated
taking ionic compounds and temporarily separating them
not a chem chg, but is a physical chg (dissolving)
complete ionic equation - an equation that shows dissolved ionic compounds as dissociated free ions
spectator ion - and ion that appears on both sides of an equation and is not directly involved in the reaction
net ion equation - equation for a reaction in solution that shows only the particles that are directly involved in the chem chg and are balanced with respect to mass and charge