Solutions
What are the 3 types of intermolecular forces relevant to the dissolution process?
1. solute-solute
2. solvent-solvent
3. solute-solvent
what is the difference between the reaction quotient and the equilibrium constant?
equilibrium constant K: concentrations of products over reactants at equilibrium
reaction quotient Q: concentrations of products over reactants at any point other than equilibrium
is water an acid or a base?
both! it is amphoteric
The Ka of HF is 7.2 X 10-4. Is this reaction said to be product or reactant favored?
Reactant favored. K<1 meaning more reactants will be present than products at equilibrium. HF is a weak acid and will not ionize completely.
Example of a buffer
any weak acid or base and its conjugate pair
Ex: NH3 and NaNH4Cl
electrolytes
What Is Le Chãtelier's principle?
if an equilibrium is stressed, the system will experience a shift in response to this stress that re-establishes equilibrium
what is the (approximate) percent ionization for a strong acid such as HCl in a solution of water?
100%
A buffer is a solution that resists changes in pH.
1. weak acid + conjugate base
OR
2. weak base + conjugate acid
What does the equivalence point on a titration curve mean?
chemically equivalent quantities of reactants have been mixed (pH is not always neutral)
The quantity of an ideal gas that dissolves in a definite volume of liquid is directly proportional to the pressure of the gas.
which law is this?
Cg = kPg
k= Henry's law constant
Cg= solubility
Pg=partial pressure
2NO(g) + Cl2(g) ⇌ 2NOCl
Kc = 4.6 x 10^4
.0500 mol NO(g), .0115 mol Cl2(g), .500 mol NOCl
volume for all is 1.00L
what direction will the reaction proceed?
will proceed forward because Qc < Kc
Which reaction will occur when HCl is placed in water?
1. HCl + H2O --> Cl- + H3O+
2. HCl + H2O --> H2Cl + OH-
3. HCl + H2O --> H3ClO
1. HCl + H2O --> Cl- + H3O+
Which is a stronger acid, H2CO3 or HCO3-? Why?
H2CO3. A molecule with a negative charge will be less inclined to lose an additional proton as its stability will decrease.
Why does the titration of a weak base with a strong acid lead to an acidic solution at the equivalence point?
A conjugate acid will be produced during the titration, which then reacts with water to form hydronium ions, lowering the pH.
20 degrees C
Pg= 101.3 kPa
Cg= 1.38 x 10^3 mol/L
What is Cg when Pg= 20.7 kPa
Cg= 2.82 x 10^-4
1. find K
2. find Cg for new Pg using k constant and equation
Kc = 4.1 x 10^-4
N2(g) + O2(g) ⇌ 2NO(g)
[N2]= .036 M
[O2]= .0089M
[NO]^2=?
3.6x10^-4
Kw = [H30+][OH-]= 1.0x10-14 (ionization constant of water)
What is the concentration of OH- if the concentration of H3O+ is 2.0x10-6?
5.0x10^-9
0.100 M HBr is dissolved in water. What is the resulting pH?
pH = 1
HBr is a strong acid. Strong acids ionize completely. So [H+] is said to be 0.100 M.
pH = −log ([H+]) = −log (0.100) = 1
Sketch a titration curve of HF with NaOH. Mark the equivalence point and clarify if the solution will be basic, neutral, or acidic at that point.
basic at equivalence point
what is the freezing point of the solution of 0.724g CaCl2 and 174g H2O ?
Freezing point of water is 0 degrees C
Find mols of solute in order to find molality
Need to find i →
When CaCl2 dissociates, 3 mols of ions are being dispersed into the system, Ca2+, Cl-, Cl-
Or : 3(6.57X10-3)/6.57X10-3) = 3
→ so, i=3
Then find molality
Then, Use 𝚫Tf = iKfm
Subtract change from 0 degrees c
A: -0.210 degrees C
N2 (g) + 3H2 (g) --> 2NH3 (g) ΔH = -92.0 kJ/mol
What are three ways you can increase the amount of ammonia gas produced?
1. Remove NH3 as it is formed
2. Lower the temperature of the reaction
3. Increase pressure on the system
What is the % ionization for .100M C2H3O2?
Ka=1.8x10^-5
C2H3O2(aq) + H20(l) ⇌ H3O+(aq) + C2H2O2-(aq)
hint: acetic acid is very weak
1.3%
Ka = 1.8 x 10^-5 = x^2/(.100) *x is so small it is negligible
[H3O+] = 0.0013
[H3O+]eq/[acetic acid]i = .0013/.100 x 100 = 1.3%
What is the pH of a 40.0 mL solution that is 0.19 M in CN− and 0.29 M in HCN?
The Ka for HCN is 4.9×10−94.9×10−9.
pH = 8.13
This solution is a buffer.
1. Determine the [H+] concentration by substituting the concentrations of the weak base (CN−) and conjugate acid (HCN) into the Ka expression.
2. Convert [H+] to pH.
A buffer solution is made using a weak acid, HA, with a pKa of 4.60. If the ratio of [A−] to [HA] is 0.10, what is the pH of the buffer?
pH = 3.60
Insert the pKa and concentration ratio into the Henderson–Hasselbalch equation to calculate the pH.
pH=pKa+log([A−]/[HA])
pH=4.60+log(0.10)=3.60