Chem test 9th grade Flashcards
What is atomic mass
It is how many grams in a mole
How much is one mole
a collection of 6.02 x 10^23 things
Is a mole a molecule
no
Who discovered moles
Avogadro
what is a molecule
It is a combo of two or more atoms held together by chemical bonds
What do subscripts tell you
how many of each atom there are in one molecule
how do you go from number of particles to number of moles
divide by avogadros number
What is avogadros number
6.02 x 10^23
how do you go from number of moles to mass
multiply by molar mass
how do you go from mass to number of moles
divide by molar mass
how do you go from number of moles to number of particles
multiply by avogadros number
moles to litres
do moles x 22.4
litres to moles
litres / 22.4
1 mole of gas =
22.4 litres
molar mass number =
atomic mass number
to balance equations, you must
add coefficients to make all elements equal on either side
what are ions
atoms with a positive or negative charge due to the loss/gain of electrons
what is an covalent bond
elements that share electrons
What is an ionic bond
when elements lose/gain an electron
What is electronegativity
how strong an atom is (can it steal your electrons) The measure of an atom’s ability to attract electrons to itself
What is the strongest and weakest electronegativity
4 is strongest, 1 is weakest
Why do covalent bonds occur
Because the two elements are too similar in electronegativity and therefore can’t steal so therefore share
what is relative atomic mass?
the average atomic mass of all the naturally occurring isotopes of a given element
How is atomic mass measured
in Amu which is 1/12 the mass of carbon 12
How many atoms are there in 12 grams of carbon 12?
there are 6.02 x 10^23 atoms
To find the molar mass of a compound do
multiply the subscript by the atomic mass of all the elements
then add together all the numbers
How is energy increased
temperature
What conditions are needed for a reaction to occur
minimum kinetic energy
collide with each other
be facing the correct way when they collide
What does higher concentration do
when theres higher concentration, there are more particles to collide meaning more collisions.
greater chance of successful collisions results in more product made in the same time
What does collision theory state
that for a reaction to occur, the particles involved must collide with the correct orientation and sufficient energy
Higher surface area means
more room for reaction to occur. The larger the surface area, the faster the reaction occures
What element are humans primarily made from
carbon
what happens after two half lives and after three?
after one you get 1/2, after two you get 1/4, after three you get 1/8 and so on
What does endo stand for
inside (cold
What does exo stand for
outside (hot)
What does thermic stand for
heat
What is activation energy
the minimum amount of energy colliding particles need for a collision to be successful and for a reaction to occur
what is an exothermic reaction
a chemical reaction during which heat is released into surroundings
What is an endothermic reaction
a chemical reaction during which heat is absorbed form the surroundings
What does an exothermic graph look like
It is flat where the reactants are
there is a curve up then down
then the products are flat below where the reactants where
What does an endothermic graph look like
reactants are flat line
curve up to products
products are flat line above reactants
x axis is reaction progress
y axis is potential energy
What is a catalyst
a substance that increases the rate of a chemical reaction without itself undergoing any permanent change, by lowering the activation energy
what is the rate of chemical reactions
speed at which reactants turn into products
how do you calculate the average rate of reactants
either
change in mass of reactants used / time taken
change in mass of products used / time taken
answer is in cm^3 per second
time is always seconds
what does a graph look like when you use quantity of reactants
y axis is mass of reactants
x axis is time
line curving down in a slide
What does a graph look like when you use the volume of product
y axis is volume of products
x axis is time
line curves upward in a rainbow
What are factors that affect rate of a chemical reaction
temperature
surface area
concentration/pressure
catalyst
If particles don’t have enough energy then…
nothing happens
Rate also depends on
frequency of collisions
amount of energy particles have
How does temp affect rate of chemical reaction
particles gain more energy which causes them to move faster, and collide with more energy
How does pressure/concentration affect rate of chemical reaction
as pressure/concentration increases, there are more particles per unit of volume, making collisions more frequent
How does surface area affect rate of chemical reaction
higher surface ares means more area for collisions to occur which means frequency of collisions would be higher
How does a catalyst affect rate of chemical reaction
catalysts lower activation energy creating a higher proportion of successful collisions
When are reactions the fasted?
At the beginning, then they slow down until they stop
How do you tell if one reaction is faster than the other
Whichever line is steeper is the faster reaction
how to determine percentage yield
(actual yield / theoretical yield)100
how to find actual yield
(percentage x theoretical)100
Why does percent yield exist
- reactants might not all react or begins to reverse
- slow reaction and not all reacts
- side reactions
- some is lost during the process
- spilled
- left in the container
relative vs molar mass
relative - mass of a single molecule
molar mass - mass of a mole
triangles
grams / moles x molar mass
particles / moles x 6.02 x 10^23
