exam 3 Flashcards
Molarity
the moles of solute per liter of solution.
M: mol/Liter
what is the molality of a solution where 333 of KHCO3 is dissolved in enough water to make 10 L of solution?
- Convert g of KHCO to moles of HCO3
(333g KHCO3) x (1 mole KHCO3/100.1 g KHCO3) : 3.33 mol - Use this value as the numerator in the defining equation for molarity
3.33 mol/10L: 0.333 M KHCO3
what mass in g of NaCl is requires to prepare 0.5 : of typical over the counter saline solution (0.15 M NaCl)?
- Use molality as a conversion factor to calculate mole of NaCl
(0. 5 L) x (0.15 mol NaCl/1 L solution): 0.075 mol NaCl - Use the molar mass to calculate g of NaCl
(0. 075 mol NaCl)x(58.5 g NaCl/1 mol NaCl): 44 g
Concentrated HCl is 12.0 M HCl. what volume in mL of this solution contains 0.425 mol HCl?
- Use the molality as a conversion factor to calculate mols of
moles of solute/molality: 0.425 mol HCl/12.0 M HCl
Concentrated HCl is 12.0 M HCl. what volume in mL of this solution contains 0.425 mol HCl?
- Use the molarity as a conversion factor to calculate mols of
moles of solute/molality: 0.425 mol HCl/12.0 M HCl: 0.0354 L
Percent concentration by volume
volume of solute/volume of solution (100%)
ex: (120 ml of oil/4000 ml of solution) x 100%: 30%
Percent concentration by mass
mass of solute/mass of solution (100%)
Ex: what is the % by mass of NaCl if 25.5 g of it is dissolved in 425 g of water?
25.5 g NaCl/(25.5g+425g) x100%: 5.66%
Ionic bonds
strongest force that holds matter in the condensed state.
electronegativity differences determine whether compounds contain polar or non polar covalent bonds in molecular compounds or ionic bonds in ionic compounds.
INTRAMOLECULAR forces action
keep the elements together in their molecules
INTERMOLECULAR forces action
between molecules. Determines how molecular compounds interact with each other.
intermolecular forces
DIPOLES
the separation of the charges in the molecules such as in the ionic bond or the unequal sharing of the electrons such as in the polar covalent bonds.
Dipole forces
polar molecules exist as dipoles. These oppositely charged ends will attract each other
Hydrogen bonds
when a hydrogen atoms is covalently bonded to a highly electronegative atoms like nitrogen, oxygen or fluorine, it can exhibit an additional polar attraction
Dispersion Forces
nonpolar molecules exhibit a dynamic weak induced dipole due to continuos movement of the electrons. The strength of the forces increases with molecular weight. The resulting dipole attractions are called cores or LONDON DISPERSION FORCES. They can exist between any 2 particles whether polar, non polar or ionic.
Types of intermolecular forces
dipole to dipole (ionic and polar covalent molecules)
hydrogen bond forces (molecules with hydrogen and high electronegativity elements >0.5)
dispersion forces (ionic, polar
Types of intermolecular forces
dipole to dipole (ionic and polar covalent molecules)
hydrogen bond forces (molecules with hydrogen and high electronegativity elements >0.5)
dispersion forces (ionic, polar)
solution
a homogeneous mixture of 2 or more substances
solute
a substance that is dispersed in a solution
solvent
the substance doing the dissolving. Present in greatest quantity
Like dissolves like
solutions from most readily when both the solute and solvent have similar intermolecular forces.
ionic substances
dissolve in water through ion dipole interactions. In non polar solvents there are basically no dipole forces that can attract the ionic substances and therefore break it apart (dissolve)
solvent: ionic
solute: polar covalent
solute will dissolve in solvent
Kinetic molecular theory of a gas
- particles of a gas are in rapid constant motion
- The gas particles are tiny compared to the distance between them
- there is little attraction between the particles of a gas
- collisions between gas molecules are perfectly elastic
- temperature is a measure of the average kinetic energy of a gas molecule.
Boyle’s law
At a constant temp, the volume of a gas is inversely proportional to its pressure,
V1P1: V2P2
Charle’s law
At a constant pressure, the volume of a gas is directly proportional to its absolute temperature.
V1/T1: V2/T2
Avogadro’s law
at a fixed temperature and pressure, the volume of a gas is directly proportional to the amount of gas.
v1/n1: V2/n2
a mole of any gas occupies 22.4L @ STP
Calculate the density of a nitrogen gas and methane gas, both at STP
28g N2/1 moleN2 x 1 mole N2/22.4 LN2: 1.25g/L
- g CH4/1 mole CH4 x 1 mole CH4/22/4 LCH4: 0.714 g/L
combined gas law
P1V1/T1: P2V2/T2
Ideal gas Law
PV: nRT
R: 0.0821 L atm/mol (K)
n: moles
Ideal gas Law
PV: nRT
R: 0.0821 L atm/mol (K)
n: moles
Blue Litmus paper turns
red in acid
Red litmus paper turns
blue in alkaline
A base and an acid form (NaOH+HCl)
water and salt
Acids
molecular substance that ionizes in aqueous solution to produce hydrogen ions (H+)
Bases
a substance that produce hydroxide ions (OH-)
HNO3 forms
H+ (aq) + NO3 (aq_
KOH forms
K+ (aq) + OH- (aq)
Neutralization
when an acid reacts with a base, the properties of each are neutralized and the products are water and salt.
Limitations of the Arrhenius theory
H+ ions don’t exist in water solution. Protons react with water to form hydronium ions (H30)
H++H20—>H30
-doesnt explain the basicity of ammonia and similar compounds.
-it only applies to reactions in aqueous solutions
Bronted Lowry Theory
Acid: proton donor
HCl + H20—> H30++Cl-
Base: proton acceptor
NH3 + H20—>NH4++ OH-
Salts
ionic compunds composed of cations other than hydrogen and anions other than hydroxide ( AgNO3, SnF2, etc)
anhydride
means without water
nonmetal oxides are acidic anhydrides
nonmetal oxides + water: acid
ex: SiO+H20: H2SiO2
metal oxides
are basic anhydrides
metal oxides+H20: base
ex: MgO+H20: Mg (OH)2
strong acids
ionize completely in water solution
less than 2
weak acid
only partially ionize in water solution
strong bases
ionize or dissociate completely in water solution
more than 12
Weak bases
only partially ionize in water solution
why is ammonia a base?
because it accepts a proton from water
the amount of acid or base in a solution is determined by
careful neutralization
concentration of H+
1x10-0: pH of 0
1x10-6: pH of 6
conjugate base
the Cl- from
HCl—> H++ Cl-
conjugate acid
anything that is not OH-
Buffer solutions
contain a weak acid and its conjugate base.
Capable of maintaining a nearly constant pH when small amount of acid or base are added.
