Lab Guide 2: pH and Buffers
Acids on the pH scale
0-6
What is the molar concentration of H+ in pure water?
1x10^-7
What is the molar concentration of OH- in pure water?
1x10^-7
What is the product of the molar concentrations of H+ and OH- in pure water?
1x10^14
If we say that one solution has 100 times as many hydrogen ions as another solution, how many pH units of difference exist between the two solutions?
2 units of pH
Bases on the pH scale
8-14
Bases
A solution that increases the number of OH- ions and decreases the number of H+ ions
What is a buffer composed of?
An acidic-base conjugate pair of a weak acid or a weak base in a solution
Reactants when water ionizes
H+ + OH -
What are the OH-, H+, and pH of a 0.01 M Solution of NaOH?
H+ = 10^-2 OH- = 10^-12 pH=2
What is the H+ of a solution whose pH is 8? What is [OH-] of this solution?
H+ concentration is 10^-8; OH- concentration is 10^-6
Example of a weak acid
H2CO3 (carbonic acid)
Example of a strong acid
HCl
Example of weak base
NH3 (ammonia)
Example of a strong base
NaOH (sodium hydroxide)
Write the equation for the neutralization of NaOH by HCl
NaOH + HCl → Na+ +OH- + H+ + Cl- → NaCl + H20
What are the OH, H, and pH of a 0.1 M solution of KOH?
OH= 10^1 H= 10^-13 pH=13
If solution A contains 1x10^-6 M H+ ions and solution B contains 1x10^-8 H+ ions, which solution contains more H+ ions?
Solution A has more H+ ions; Solution B is more basic and therefore has more OH- ions than H+ ions
What happens to pH when you increase H+ ions?
The acidity increases because there is a decrease in OH-
What happens to pH when you decrease OH- ions?
The solutions gets more basic because there are less H+ ions
HCl ionizes completely in water. What is the H+ of a 0.01 M Solution of HCl? What is the pH
[H+}= 10^-2; pH is 2
pH
a measure of the concentration of hydrogen ions in an aqueous solution -- how acidic or alkaline the solution is
Acids
a substance that increases the number of H+ ions and decreases the number of OH- ions
Is the hydrogen ion concentration of a pH 3.8 solution higher or lower than that of a solution with a pH of 6.2?
the 3.8 pH has a higher concentration of hydrogen ions because it is more acidic, so it has more H+ and less OH-
HA is a hypothetical acid that ionizes 10% in solution. What is the H+ of a 0.01 M solution of HA? What is its pH?
the H+ is 10^-3, the pH is 3