10 Questions
Which of the following is true regarding the pH scale?
All of the above.
Which of the following acids is responsible for the sour taste in tomatoes?
Oxalic acid
What is the primary cause of acid rain?
Emissions of sulfur dioxide and nitrogen oxides from industrial processes and fossil fuel combustion.
Which of the following is a property of bases?
They accept hydrogen ions (H+) in aqueous solutions.
Which of the following salts belongs to the same family as sodium chloride?
Potassium chloride
What is the purpose of adding lime (calcium oxide or calcium hydroxide) to soil by farmers?
To decrease the acidity (or increase the basicity) of the soil.
Which of the following acids is responsible for the sting of ant and nettle stings?
Methanoic acid
What is the primary reason for the importance of maintaining a specific pH range in the human body?
To ensure proper enzyme function and cellular processes.
Which of the following is a common example of an acid-base reaction in everyday life?
Baking soda (sodium bicarbonate) reacting with vinegar (acetic acid) to produce carbon dioxide gas.
What is the primary role of acids in the human body?
To aid in digestion by breaking down food in the stomach.
Study Notes
pH of Common Substances
- pH of saliva before meal is around 7, and after meal is around 8
- pH of lemon juice is around 2
- pH of carrot juice is around 5
- pH of coffee is around 5
- pH of tomato juice is around 4
- pH of tap water is around 7
- pH of 1M NaOH is around 14
- pH of 1M HCl is around 1
Strength of Acids and Bases
- Acids that produce more H+ ions are strong acids, and those that produce less H+ ions are weak acids
- Bases that produce more OH- ions are strong bases, and those that produce less OH- ions are weak bases
Importance of pH in Everyday Life
- The human body works within a pH range of 7.0 to 7.8
- Living organisms can survive only in a narrow range of pH change
- Acid rain has a pH of less than 5.6 and can affect aquatic life
- Plants require a specific pH range for their healthy growth
Acids and Bases
- HCl, HNO3, etc. show acidic characters in aqueous solutions because they dissociate to produce H+ ions
- Solutions of compounds like alcohol and glucose do not show acidic character because they do not dissociate to produce H+ ions
- Aqueous solutions of acids conduct electricity due to the presence of ions
- Dry HCl gas does not change the color of dry litmus paper because it does not dissociate to produce H+ ions
- Adding water to acid is recommended to avoid local heating and splashing
- Dilution of an acid decreases the concentration of H+ ions
- Dilution of a base decreases the concentration of OH- ions
Naturally Occurring Acids
- Vinegar contains acetic acid
- Sour milk (curd) contains lactic acid
- Orange contains citric acid
- Lemon contains citric acid
- Tamarind contains tartaric acid
- Ant sting contains methanoic acid
- Tomato contains oxalic acid
- Nettle sting contains methanoic acid
pH and Hydrogen Ion Concentration
- A solution with a pH of 6 has a higher hydrogen ion concentration than a solution with a pH of 8
- A solution with a pH of 6 is acidic, while a solution with a pH of 8 is basic
- The concentration of H+ ions affects the nature of the solution, with higher concentrations making the solution more acidic
- Basic solutions also have H+ ions, but they have a higher concentration of OH- ions, making them basic
- Farmers may treat soil with quick lime, slaked lime, or chalk to adjust the pH and make it suitable for plant growth
Salts
- Salts are formed during various reactions, such as neutralization reactions
- Salts have specific properties and uses, such as potassium sulphate, sodium sulphate, calcium sulphate, and magnesium sulphate
- Salts can be grouped into families based on their positive or negative radicals
Test your knowledge of the pH values of various common substances like saliva, lemon juice, aerated drink, and more. Understand how pH paper can be used to determine the acidity or alkalinity of these substances.
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