Questions and Answers
Match the following solutions with their pH ranges:
Gastric juices = 1-2 Vinegar = 2-3 Pure water = 7 Blood = 7.4
What color does litmus indicator turn in a strong acidic solution?
What is the product formed when sulfur dioxide reacts with sodium hydroxide?
What affects the growth and development of plants in relation to soil?
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Acidic oxides react with alkalis to produce a salt and water.
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The pH meter measures pH ______.
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What is the neutral pH value?
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Which of the following substances is an example of a basic oxide?
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Which indicator turns pink in a strong alkaline solution?
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What happens when calcium oxide reacts with nitric acid?
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What do acids produce in aqueous solution?
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HCl gas is considered an acid.
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Which of the following acids is an organic acid?
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Acids dissolve in water to form solutions that can conduct electricity.
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What happens when an acid reacts with a metal?
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What is the product of an acid reacting with carbonates?
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What is the name given to the reaction between an acid and a base?
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Which of the following is a characteristic property of alkalis?
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What ion do alkalis produce in aqueous solution?
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Which ion is produced when sulfuric acid is neutralised by a base?
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What is the pH scale used for?
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Strong acids are completely ionised in aqueous solution.
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Concentration and strength of an acid are the same.
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Study Notes
Acids
- Acids are substances that produce hydrogen ions (H+) in aqueous solutions.
- Properties of acids: sour taste, turn blue litmus paper red, and can conduct electricity when dissolved in water.
- Acids react with metals, bases, and carbonates to produce salts, water, and gases (such as hydrogen).
- Examples of acids include sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), and organic acids like citric acid and lactic acid.
- Specific reactions include:
- Magnesium + sulfuric acid → magnesium sulfate + hydrogen.
- Zinc + hydrochloric acid → zinc chloride + hydrogen.
- Acids are neutralized by bases, resulting in salt and water.
Bases and Alkalis
- Bases are metal oxides or hydroxides that react with acids, producing salts and water in a neutralization reaction.
- Alkalis are soluble bases that produce hydroxide ions (OH-) in aqueous solutions, e.g., sodium hydroxide (NaOH).
- Common bases include sodium oxide, zinc oxide, and calcium hydroxide.
- Reaction examples:
- Sulfuric acid + copper(II) oxide → copper(II) sulfate + water.
- Hydrochloric acid + sodium hydroxide → sodium chloride + water.
- Alkalis feel soapy, taste bitter, and turn red litmus paper blue.
Strength and Concentration
- Strong acids completely ionize in aqueous solutions (e.g., HCl).
- Weak acids only partially ionize (e.g., acetic acid).
- Acid strength refers to ionization extent, while concentration indicates the amount of acid in a solution.
- A strong acid remains fully ionized regardless of its concentration.
The pH Scale
- The pH scale ranges from 0 to 14, indicating whether a solution is acidic, neutral, or alkaline.
- A lower pH (0-6) indicates higher acidity, while a higher pH (8-14) indicates alkalinity.
- pH can be measured using indicators, pH sensors, or meters.
- Indicators change color based on acidity or alkalinity:
- Litmus: red in acid, blue in alkali.
- Methyl Orange: red in acid, yellow in alkali.
- Phenolphthalein: colorless in acid, pink in alkali.
- Universal indicators can help assess a solution’s pH visually by comparison with a color chart.### pH Measurement
- pH probes are used to measure the acidity or alkalinity of solutions.
- Results are displayed digitally for accurate readings.
Importance of Soil pH
- Soil pH significantly influences plant growth and development.
- Potatoes thrive in pH range 5.5–6.5.
- Cabbages prefer a higher pH of 7.5–8.5.
- Most plants favor neutral or slightly acidic soils for optimal growth.
Managing Soil pH
- Soil pH may become unsuitable due to excessive fertilizer use or environmental issues (e.g., acid rain).
- To treat soil acidity, apply:
- Calcium oxide (quicklime)
- Calcium hydroxide (slaked lime)
- This process, known as "liming," neutralizes soil acidity.
Types of Oxides
- Oxides are compounds formed from oxygen.
- Classified into four categories: acidic, basic, amphoteric, and neutral.
- Metallic oxides are ionic compounds, while non-metallic oxides are covalent compounds.
Acidic Oxides
- Typically non-metallic and often exist as gases at room temperature.
- Dissolve in water to form acids.
- Examples include:
- SO2 → H2SO3 (sulfurous acid)
- SO3 → H2SO4 (sulfuric acid)
- CO2 → H2CO3 (carbonic acid)
- Acidic oxides react with alkalis to produce salts and water.
Basic Oxides
- Composed of metals and solid at room temperature.
- React with acids, producing salts and water.
- Some dissolve in water to form alkalis, e.g.:
- MgO, CuO, ZnO as insoluble; Na2O, K2O as soluble.
- Examples of reactions include:
- CaO + HNO3 → Ca(NO3)2 + H2O (produces calcium nitrate)
- Na2O + HCl → NaCl + H2O (produces sodium chloride)
Amphoteric Oxides
- Can react with both acids and alkalis, behaving as both.
- Examples include ZnO, PbO, Al2O3.
- Reactions with alkalis produce salts:
- Al2O3 + NaOH → NaAlO3 (sodium aluminate)
- PbO + NaOH → Na2PbO2 (sodium plumbate)
Neutral Oxides
- Insoluble in water, exhibit neither acidic nor basic properties.
- Examples include H2O (water), NO (nitric oxide), and CO (carbon monoxide).
Reactions of Zinc Oxide
- ZnO reacts with hydrochloric acid to form zinc chloride and water.
- It also reacts with sodium hydroxide to form sodium zincate and water, demonstrating its amphoteric behavior.
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Description
This quiz focuses on Chapter 11, which covers Acids and Bases, essential concepts in chemistry. You'll explore definitions, properties, and characteristics of acids, bases, and the pH scale. Test your understanding and reinforce your knowledge of these fundamental topics in chemistry.
