Question

What is acidity and what are the compounds controlling it?

Acidity is a measure of the concentration of hydrogen ions (H⁺ or protons) in a solution. We use pH (potential of H+) as a scale of acidity and this can be calculated as below:

pH = -log₁₀[H⁺] = log₁₀ (1/[H⁺])   Q1. Figure 10.3 shows you a range of pH in some common liquids. Pick 2 liquids (one each from acidic and basic solutions) and compare the molarity of [H⁺] in each solution by using the pH equation above. Which one has more [H⁺]?

Q2. What is the pH range of natural rainwater and acid rain? Why do you think natural rainwater is not neutral? Write down the relevant reaction related to the acidity of natural rainwater.

What is the cause of acid rain and what are the effects?

Q3. Figure 10.4 is a map of the rainwater pH in the U.S. What was the main cause of acid rain and what is the reaction involved? Do you see any regional trends of rainwater pH in the map? What may be the cause of driving this?

Q4. The reactions below show the reactions of 3 main gases (i.e., SO₂, CO₂, NO₂) that are responsible for making rainwater more acid. What are the sources of these gases? State at least one for each gas.

Q5. What are the effects of acid rain (at least 3!) and how can we reduce this?

Q6. What has been done in the US to reduce acid rain?

where, [H+] = molarity (M, moles

What is acidity and what are the compounds controlling it? Acidity is a measure of the concentration of hydrogen ions (H or protons) in a solution. We use pH (potential of H+) as a scale of acidity and this can be calculated as below: pH = -log10[H+] = log10 (1/[H+]) where, (H+) = molarity (M, moles of H+ per liter of solution) Natural rainwater (5-5.6) Acid rain, fog (2-5.6) Sea water (7.8-8.3) pH 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 AM Battery Lemon Apples acid juice (3.1) (1.0) (2.2) Distilled water (7.0) Ammonium hydroxide NH OH(aq) Lye | |NaOH(aq) Vinegar (11.1) CH3COOH(aq) (2.8) Milk (6.6) Baking soda NaHCO3(aq) (8.2) Slaked lime Ca(OH)2(aq) (12.4) More acidic More basic or alkaline Figure 10.3. Diagram of pH scale and pH levels of selected solutions.

Answer 1

Q.1.

Substancees having pH less than 7 are acidic , more than 7 is basic and with pH = 7 are neutral .

pH = -log[H^+]

Therefore , [H^+] = 10^-pH

Substances with [H^+] > 1×10^-7M , are acid

And with [H^+] < 1×10^-7M , are basic . With [H^+] = 1×10^-7M are neutral.

Two liquids choosen from figure are : battery acid having pH = 1

And NaOH(aq) Lye having pH=13 .

[H^+] for battery acid = 10^-pH = 10^-1

For NaOH , [H^+] = 10^-13 .

Hence [H^+] is more for battery acid .