Chemical Reaction Basics
#1- what is a chemical reaction?
A chemical reaction is when one or more substances undergo a chemical change to form a new substance (reactants combine to form products)
#5- what is a word equation?
word- uses full words, does not include ratios (aka coefficients), usually does not include state of matter
11- How many hydrogen and oxygen atoms on each side? (see study guide)
Reactant side-
H-4
O-2
Product side-
H-4
O-1
#20- what does "endo" mean in endothermic reaction?
endo means "in"/"inside"- in endothermic reaction, it means that heat is "drawn in"- the product is COLDER than the reaction
#2- List 3 ways we can represent chemical rxns
word, skeletal, and chemical equations
#6- what is the drawback of a skeleton equation?
No coefficients- Doesn't tell you how many moles (aka how much) of each substance you need for a balanced equation.
12- Balance the following equation:
___N2+___H2-->___NH3
N2+3H2-->2NH3
#16- define an endo and exothermic rxn
endothermic- energy of products is lower than reactants (colder)
exothermic- energy of products is HIGHER than reactants (gives off heat- products are warm/hot)
#4- what do the following symbols mean in a chemical equation?
+ , (l) , -->
plus/and (separates two products or reactants)
liquid
yields/produces
#7- Write a skeleton equation for the following word equation:
Hydrogen and bromine gasses react to yield hydrogen bromide
H2(g)+B2(g)-->HBr(g)
#14- Chemical reactions occur in the following bread picture. What factor is responsible for that?
Temperature
#17- give one real life example of an endothermic rxn
photosynthesis!
#3- what are the unique characteristics of each way we represent chemical equations? (basically, describe each type)
word- uses full words, does not include ratios (aka coefficients), usually does not include state of matter
skeletal- basically this is the "unbalanced" form of your chemical equation. Does not include coefficients, INCLUDES state of matter for all reactants/products.
chemical equation- balanced skeletal equation; includes coefficients, subscripts, etc. Often also includes states of matter.
#10- What is the coefficient and subscript in
3Br2
3- coefficient
2-subscript
WILD CARD!
List four factors that affect reaction rate
temperature
concentration
pressure
surface area
#19-What is the equation for an exothermic rxn?
reactants --> products + energy
#8- What are coefficients and subscripts in a chemical equation? Give an example of each.
Coefficients- large numbers in front of an atom/molecule. This tells us how many "sets" of a molecule we have and is the number we change when balancing an equation.
Subscript- the small # to the bottom right of a molecule- determines the IDENTITY of a molecule (remember water vs. hydrogen peroxide). We NEVER change this when balancing an equation!
Examples:
#9- Do we need to change subscripts or coefficients to balance the equation? Why?
Coefficients- changes the # of atoms/molecules, but NOT the identity of the molecules. We never change the subscripts because it changes the identity!
#13- What is reaction rate? Make sure to include the factors that affect rxn rate in your response
The speed at which a reaction occurs. Influenced by temperature, pressure, concentration, and surface area. Can ALSO be influenced by stirring!
#15-What type of reaction is occurring in the picture below?
combustion- EXOTHERMIC