5B2 pH Flashcards
Perform pH, pOH, and ion concentration calculations for acidic and basic solutions. (39 cards)
What does ‘pH’ stand for?
Potential of hydrogen
The pH of a solution indicates the concentration of hydrogen ions (H⁺) in a solution.
Which scientist introduced the concept of pH?
Søren Peter Lauritz Sørensen
He introduced the pH scale in 1909 while working for a beer company.
Which scale is used to measure the acidity or basicity of a solution?
The pH scale
The pH scale ranges from 0 to 14.
Values below 0 or above 14 can occur, but they are rare.
Define:
pH
mathematically
pH = -log [H⁺]
This equation relates pH to the hydrogen ion concentration, where [H⁺] represents the concentration of hydrogen ions.
What is the pH of a neutral solution?
7
Neutral solutions have equal H⁺ and OH⁻ ions.
Fill in the blank:
Acids have pH values ____ than 7.
less
Acids are represented by pH values from 0 to 6.
Fill in the blank:
Bases have pH values ____ than 7.
greater
Bases are represented by pH values from 8 to 14.
Which equation is used to calculate pOH?
pOH = -log [OH⁻]
This equation calculates pOH based on hydroxide ion concentration.
How do you calculate pOH from pH?
pOH = 14 - pH
The sum of pH and pOH in a solution is always 14.
How does the pH scale relate to the concentration of H⁺ ions?
It is logarithmic; each pH unit change represents a tenfold change in H⁺ ion concentration.
For example, a pH of 6 has ten times the H⁺ ion concentration of a pH of 7.
What is the estimated pH of a solution with [H⁺] = 4.6×10^-5?
Between 4 and 5.
The exponent provides a rough estimate of the pH range.
True or False:
A solution with pH=2 is a strong acid.
True
Strong acids have pH values closer to 0.
What does [OH⁻] represent?
The concentration of hydroxide ions in moles per liter (M).
It quantifies the basicity of a solution.
Which pH value range represents strong bases?
12–14
Strong bases are far from the neutral value of 7.
True or False:
pH can be a negative number.
True
Extremely high [H⁺] can result in negative pH values.
What does the negative sign in the pH formula accomplish?
It makes the pH value positive when the H⁺ concentration is less than 1.
Since [H⁺] is often less than 1, the logarithm of [H⁺] is negative, and the negative sign inverts it.
What happens to the pH when H⁺ ion concentration increases?
It decreases.
The pH scale inversely reflects the concentration of H⁺ ions; higher [H⁺] means lower pH.
Calculate the pH of a solution [H⁺] = 10^-5.
pH = 5
The pH is the negative logarithm of the hydrogen ion concentration.
pH = -log [H⁺] = -log(10^-5) = 5
What is the pH of a solution with [H⁺] = 10^-7?
pH = 7
This is the pH of neutral water, where [H⁺] and [OH⁻] are equal.
What type of relationship does a logarithmic scale represent?
A non-linear relationship between data.
Each unit change on the x-axis corresponds to a tenfold change on the y-axis. This is true for the pH scale or the Richter scale that measures earthquake intensity.
Fill in the blank:
[H⁺] multiplied by [OH⁻] equals _____.
1×10^-14
This is the ion product of water (Kw).
Fill in the blank:
The lower the pH value, the _____ the acidity.
higher
Lower pH indicates higher [H⁺].
What happens to basicity as pH decreases?
It decreases.
A lower pH indicates lower [OH⁻].
What is the pH of a solution with [H⁺]=1×10^-3?
pH = 3
This is calculated using pH = -log [H⁺].
