What do you have to do if you want to do a calculation regarding pH or concentration of weak acids or bases?
What is an ICE box?
100
This is the purpose of a titration.
What is to determine an unknown concentration?
100
This is why buffers are important.
What is they resist changes in pH?
200
This is pKw at 25degC.
What is 14?
200
This is the pOH of a 0.013M solution of NaOH.
What is 1.89?
200
This is the equilibrium equation and Keq for NO2-.
What is NO2(-) + H2O <-> HNO2 + OH-
Keq=Kb=10^-14/4.6x10^-4 = 2.2x10^-11
200
This is the pH of the titration point when a weak acid and strong base are mixed.
What is greater than 7?
200
This is how to create a buffer.
What is create a solution with a substantial amount of a weak acid and its conjugate base?
300
This is the equilibrium reaction that Kw is the equilibrium constant for.
What is 2H2O(l) <-> H3O+ + OH-?
300
This is the pH of a 0.0015M solution of NaOH.
What is 11.18?
300
This is the concentration of H3O+ of a 1.0M solution of CH3COOH.
I'll start it for you...
CH3COOH + H2O(l) <-> H3O+ + CH3COO- Ka=1.8x10^-5
What is 0.0042M?
CH3COOH H3O+ CH3COO-
I 1.0 0 0
C -x +x +x
E 1-x x x
Ka=[H3O+][CH3COO-]/[CH3COOH]
1.8x10^-5 = x^2/(1-x) [assume x<<1]
1.8x10^-5=x^2/1
x=0.0042M
check... 0.0042/1=0.42%<5%
300
This is the concentration of NaOH when 25.00mL of NaOH are titrated with 13.42mL of 0.20M HCl.
What is 0.11M NaOH?
13.42mL*(1L/1000mL)*(0.20mol/L)*(1mol NaOH/1mol HCl) = 0.0027mol NaOH
0.0027mol/ 25.00mL * (1000mL/L)=0.11M NaOH
300
This is one of the pollutants that creates acid rain.
What is NOx or SOx?
400
This is the concentration of OH- if the concentration of H3O+ is 10^-3 and Kw is 10^-10 (this reaction is not occurring at 25degC).
What is 10^-7?
400
This is the concentration of a solution of HCl with pH=3.14
What is 7.2x10^-4?
400
This is the concentration of H2S required to make a solution with pH=3.00.
H2S + H2O(l) <-> H3O+ + HS- Ka=9.1x10^-8
What is 11M
pH=3... [H3O+]=10^-3=0.001
H2S H3O+ HS-
I x 0 0
C -0.001 +0.001 +0.001
E x-0.001 0.001 0.001
Keq=[H3O+][HS-]/[H2S]
9.1x10^-8=(0.001)^2/(x-0.001)
x-0.001=(0.001)^2/(9.1x10^-8)
x-0.001=11
x=11
400
This is the indicator you should use if the pH at the titration point is 7.
What is answers may vary (we use phenolphthalein)?
400
This is a natural application of a CO2 / HCO3- buffer.
What is blood or lakes?
500
The equilibrium equation for water is
2H2O(l) + energy <-> OH- + H3O+
This is how Kw will change as temperature increases.
What is as temperature increases, the equilibrium shifts to the right, so Keq=Kw increases (and pKw decreases).
500
This is the concentration of OH- in a solution with pH=2.00
What is 10^-12?
500
This is the pOH of a solution of 2.0M CN-.
CN- + H2O <->
What is 2.19?
CN- + H2O <-> HCN + OH-
CN- HCN OH-
I 2 0 0
C -x +x +x
E 2-x x x
Keq=Kb=10^-14/4.9x10^-10=2.0x10^-5
Kb=[HCN][OH-]/[CN-]
2.0x10^-5=x^2/(2-x) (assume x<<2)
2.0x10^-5=x^2/2
4.0x10^-5=x^2
0.0063M=x
check that assumption was correct... 0.0063/2 = 0.3%<5%
pOH=-log(0.0063)=2.19
(pH=14-2.19=11.81)
500
This is the concentration of HCl if 25.00mL of HCl are titrated with 8.70mL of 2.00M Ba(OH)2