Comparing Acid Rain Acidity Using pH Scale
The pH scale measures the acidity or alkalinity of a solution. It is a logarithmic scale, meaning each whole number change represents a tenfold change in acidity.
Specifically, a decrease of 1 pH unit signifies a 10 times increase in acidity (hydrogen ion concentration, [H+]). Conversely, an increase of 1 pH unit means 10 times less acidity.
Calculating Acidity Difference
We need to compare the acidity of rain with pH 4.0 to rain with pH 6.0.
- pH difference = pH of less acidic rain - pH of more acidic rain
- pH difference = $6.0 - 4.0 = 2.0$ units
Since each unit difference corresponds to a factor of 10 in acidity:
- A 2-unit difference means the acidity changes by a factor of $10^{\text{difference}}$
- Acidity factor = $10^{2.0}$
- Acidity factor = $10 \times 10 = 100$
Therefore, rain with a pH of 4.0 is 100 times more acidic than rain with a pH of 6.0.
Important Questions from Chemical Biology {p}K_a Henderson Hasselbalch
- The equilibrium dissociation constant of acetic acid is $1.74 \times 10^{-5}$ $M$. The $pK_a$ of acetic acid (rounded off to one decimal place) is ________.
- The ionic product of water at $40$ °C is $2.92 \times 10^{-14}$ $M^2$. The pH of water at $40$ °C is ________ (rounded off to 2 decimal places).
- In a lactic acid solution at pH $4.8$, the concentrations of lactic acid and lactate are $0.01$ M and $0.087$ M, respectively. The calculated pKa of lactic acid is ________ (Round off to one decimal place)
An aqueous solution of aspirin (HA) is prepared at pH 7.4. The ratio of concentration of $A^-$ and HA at equilibrium is ________ (round off to the nearest integer).
Given: $K_a$ of aspirin is $3.98 \times 10^{-4}$
- If 50 mL of 0.02 M HCl is added to 950 mL of $H_2O$, then the pH of the final solution will be _________
