HESI-A2 CHEMISTRY
HESI-A2 CHEMISTRY
Chemistry note cards for HESI entrance exam
Question Answer
Matter that has a definite shape and
... [Show More] volume solid
Matter that changes in volume with changes in temperature and pressure gas
A change of matter is when no change is made to the chemical composition of a substance.
physical
Simplest of substances and is represented by a letter or letters element
Law that states matter can neither be created nor destroyed during a chemical reaction Law of conservation of mass
The breaking of bonds and reforming of new bonds to create new chemical compounds with different chemical formulas and different chemical properties
Chemical reaction
5 main chemical reactions synthesis, decomposition, combustion, single replacement, double replacement
Chemical reaction in which 2 elements combine to form a product synthesis
Chemical reaction that is the breaking of a compound into component parts decomposition
The chemical reaction that is the reaction of a compound with oxygen combustion
Chemical reaction that consists of an active metal reaction with an ionic compound creating a new compound
single replacement
Chemical reaction involving 2 ionic compounds; the reactant yields "switched partners"
double replacement
how elements are arranged on the periodic table by their chemical properties
Number that represents the # of protons an atomic number
element has
average of the masses of each of its isotopes as they occur in nature atomic mass
Mass number - atomic number = # of neutrons in an element
Columns of the periodic table = groups
Rows of the periodic table = periods
Group IA = charge +1
Group IIA = charge +2
Group IIIA = charge +3
Group VA = charge -3
Group VIA = charge -2
Group VIIA = charge -1
Charge of noble gases 0
Positively charged ions protons
Negatively charged ions electrons
Neutral ions neutrons
# of proteins in an element = atomic number
proteins + neutrons = mass number
In reactions, atoms try to reach stable electron configurations. chemical
reactions take place in the nucleus, to obtain stable nuclear configurations.
nuclear
Word used to describe the emission of particles from an unstable nucleus. radioactivity
The particles that are emitted during radioactivity radiation
3 types of radiation alpha, beta, gamma
Radiation that is the emission of helium ions alpha
Alpha radiation particles have a charge of +2
How can penetration from alpha particles be stopped? piece of paper
Radiation that is a product of the decomposition of a neutron. It is composed of high-speed, high- energy electrons.
beta radiation
How can beta radiation particles be stopped? aluminum foil
radiation is high-energy electromagnetic radiation that lacks charge and mass.
gamma
What radiation can be stopped by several feet of concrete or several inches of lead? gamma radiation
2 types of chemical bonding ionic & covalent
What bond is an electrostatic attraction between 2 oppositely charged ions? (between metals & nonmetals)
ionic
A single bond is formed when 2 atoms share a pair of electrons. covalent
A bond is formed when 2 electron pairs are shared. double covalent
A bond is formed when 3 electron pairs are shared. triple covalent
What is the strongest type of chemical bond? What is it formed by? covalent bond; non-metals
In a covalent bond compound, if the electrons are shared equally, then the bond is .
non-polar
If electrons are not shared equally in a covalent bond, the bond is . polar
is based on the difference in electronegativity values for the elements involved
polarity
Hydrogen bonding, dipole interactions and dispersion forces. intermolecular forces
Bond that is the attraction for a hydrogen atom by a highly electronegative element. hydrogen bond
Elements fluorine, chlorine, oxygen and nitrogen are generally involved in a bond.
hydrogen
Bond that is the strongest of the intermolecular forces hydrogen
The attractions of one dipole for another dipole interactions
A is created when an electron pair in a covalent bond is shared unequally dipole
A dipole attraction is a intermolecular force. weak
The weakest of all intermolecular forces. dispersion forces
Dispersion forces are typically found in
covalent compounds. Non-polar
6.02 x 10^23 is a mole
The mass of one mole of a substance atomic mass
The part of chemistry that deals with the quantities and numeric relationships between compounds in a chemical reaction.
stoichiometry
To balance an equation, are placed in front of each component. coefficient
4 ways to increase the reaction rate increase temperature, increase surface area, increase concentrations and reactants and add a catalyst
Increasing the causes the particles to have greater kinetic energy, allowing them to move faster and have a greater chance
temperature
Accelerates a reaction by reducing the activation energy, or the amount of energy needed for a reaction to occur.
catalyst
reaction involve the transfer of electrons from one element to another redox
The loss of electrons oxidation
The gain of electrons reduction
Sum of oxidation #'s = The charge on polyatomic ions
Compounds acting as hydrogen-ion donors acids
Compounds acting a hydrogen-ion acceptor bases
pH value less that 7.0; taste sour/tart; produce h30+ (most of their formulas begin with H)
acids
Produce OH-; taste is bitter, feels slippery; conduct electricity; formulas contain OH-, pH value is greater than 7.0
bases
What characterizes a chemical reaction as combustion? adding O2
What is the change of potassium in KCl? +1 because K is found in group IA
How many electrons does an oxygen ion have 10 (it has an atomic # of 8 and is in group VIA, which has a -2 charge, which means it has 2 more electrons than he 8 protons).
How many neutrons does an atom of carbon -14 contain? 8 (take the mass #-atomic # = neutrons) 14-6=8
What is the strongest type of chemical bond? covalent bond
What is the mass of one mole of CO2? 44g/mol (C=12.011 + (15.999 x 2) =
answer)
How many moles are present in 2 moles of O2? 1.204 x 10^24 (1 mole - 6.02 x 10^23, 2
mole would be double that)
What would be the oxidation state of the sulfur atom in sulfuric acid, H2SO4? +6 [Show Less]