Chemistry Basics Quiz

Acids and Bases

• Acids are sour in taste and turn blue litmus to red, while bases are bitter and turn red litmus to blue.
• Litmus, turmeric, and certain flower petals are natural indicators that can be used to test for acids and bases.
• Synthetic indicators like methyl orange and phenolphthalein can also be used.

Properties of Acids

• Acids contain hydrogen ions (H+ or H3O+) in their molecules.
• Acids generate hydrogen gas when reacting with metals.
• The reaction of an acid with a metal can be summarised as: Acid + Metal → Salt + Hydrogen gas.
• Acids react with metal carbonates and hydrogencarbonates to produce a salt, carbon dioxide, and water.

Properties of Bases

• Bases contain hydroxide ions (OH-) in their molecules.
• Bases generate hydroxide ions when dissolved in water.
• Bases that are soluble in water are called alkalis.
• Alkalis are soapy to touch, bitter, and corrosive.

Neutralisation Reaction

• The reaction between an acid and a base to produce a salt and water is called a neutralisation reaction.
• The neutralisation reaction can be summarised as: Acid + Base → Salt + Water.
• In the neutralisation reaction, H+ ions from the acid combine with OH- ions from the base to form water.

Reaction of Acids and Bases with Indicators

• Acids turn blue litmus to red, while bases turn red litmus to blue.
• Phenolphthalein turns colourless to pink in the presence of a base.
• Methyl orange turns yellow to red in the presence of an acid.

Olfactory Indicators

• Some substances change their odour in acidic or basic media.
• Examples of olfactory indicators include onions, vanilla essence, and clove oil.

Reaction of Acids and Bases with Metals

• Acids react with metals to produce a salt and hydrogen gas.
• The reaction of a metal with an acid can be summarised as: Acid + Metal → Salt + Hydrogen gas.
• The reaction of a base with a metal is not possible with all metals.

Reaction of Metal Carbonates and Hydrogencarbonates with Acids

• Metal carbonates and hydrogencarbonates react with acids to produce a salt, carbon dioxide, and water.
• The reaction can be summarised as: Metal carbonate/Metal hydrogencarbonate + Acid → Salt + Carbon dioxide + Water.

Reaction of Metallic Oxides with Acids

• Metallic oxides react with acids to produce a salt and water.
• The reaction can be summarised as: Metal oxide + Acid → Salt + Water.
• Metallic oxides are said to be basic oxides because they react with acids to produce salts and water.

Reaction of Non-metallic Oxides with Bases

• Non-metallic oxides react with bases to produce a salt and water.

• The reaction is similar to the reaction of a base with an acid.

• Non-metallic oxides are said to be acidic in nature.### Acids and Bases

• Acids and bases can be mixed with water to form a solution, which results in a decrease in the concentration of ions (H3O+/OH-) per unit volume, known as dilution.

• The acid or base is said to be diluted in this process.

pH Scale

• The pH scale is a measure of the concentration of hydrogen ions in a solution.
• The pH scale ranges from 0 (very acidic) to 14 (very alkaline).
• A higher hydronium ion concentration results in a lower pH value.
• A neutral solution has a pH of 7.
• Values less than 7 on the pH scale represent an acidic solution, while values greater than 7 represent an alkaline solution.

Strong and Weak Acids and Bases

• The strength of an acid or base depends on the number of H+ ions or OH- ions produced, respectively.
• Acids that produce more H+ ions are strong acids, while those that produce less H+ ions are weak acids.
• Similarly, 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

• Living organisms can survive only in a narrow range of pH change.
• pH affects the survival of aquatic life in rivers and lakes.
• Acid rain with a pH of less than 5.6 can affect the pH of river water and make it difficult for aquatic life to survive.

Salts

• Salts are formed during various reactions, such as the reaction between an acid and a base.
• Salts have different properties and uses, such as pH, solubility, and chemical reactions.
• The pH of a salt solution depends on the acid and base used to form it.
• Salts can be acidic, basic, or neutral.

Preparation of Salts

• Salts can be prepared through various methods, such as the reaction between an acid and a base, or the decomposition of a substance.
• The pH of a salt solution depends on the acid and base used to form it.

Chemicals from Common Salt

• Common salt (sodium chloride) is an important raw material for various chemicals.
• Sodium chloride is used to produce sodium hydroxide, baking soda, washing soda, bleaching powder, and many more.
• These chemicals have various uses in the household and industries.

Bleaching Powder

• Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)2].
• Bleaching powder is used for bleaching cotton and linen, oxidizing agent in many chemical industries, and making drinking water free from germs.

Baking Soda

• Baking soda (sodium hydrogencarbonate) is used in the kitchen for making tasty crispy food, and for faster cooking.
• Baking soda is a mild non-corrosive basic salt.
• It is used for making baking powder, which is a mixture of baking soda and a mild edible acid.
• Baking soda is also an ingredient in antacids, and is used in soda-acid fire extinguishers.

Washing Soda

• Washing soda (sodium carbonate) is used in glass, soap, and paper industries.
• It is used in the manufacture of sodium compounds such as borax.
• Washing soda is used as a cleaning agent for domestic purposes, and for removing permanent hardness of water.

Water of Crystallisation

• Some salts, such as copper sulphate and gypsum, contain water of crystallisation.

• Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt.

• When these salts are heated, the water of crystallisation is removed, and the salt turns white or changes colour.### Plaster of Paris and Gypsum

• CaSO4.H2O (Plaster of Paris) reacts with 1H2O to form CaSO4.2H2O (Gypsum)

• Plaster of Paris is used for making toys, decorative materials, and smooth surfaces

Acids, Bases, and Salts

• Acid-base indicators are dyes or mixtures of dyes that indicate the presence of acids and bases
• Acidic nature is due to the formation of H+(aq) ions in solution, while basic nature is due to the formation of OH–(aq) ions
• When an acid reacts with a metal, hydrogen gas is evolved and a corresponding salt is formed
• When a base reacts with a metal, hydrogen gas is evolved, and a salt is formed with a negative ion composed of the metal and oxygen
• Acidic and basic solutions conduct electricity due to the presence of hydrogen and hydroxide ions, respectively

pH Scale

• pH scale measures the hydrogen ion concentration in a solution (0-14)
• Neutral solution has a pH of 7, acidic solution has a pH less than 7, and basic solution has a pH more than 7
• Living beings carry out metabolic activities within an optimal pH range

Salts and Water of Crystallisation

• Water of crystallisation is the fixed number of water molecules present in one formula unit of a salt
• Salts have various uses in everyday life and industries

Neutralisation Reaction

• Acids and bases neutralise each other to form corresponding salts and water
• Examples: HCl + NaOH → NaCl + H2O, H2SO4 + Ca(OH)2 → CaSO4 + H2O

Properties of Acids and Bases

• Mixing concentrated acids or bases with water is a highly exothermic process
• Acids and bases react with metals to form salts and evolve hydrogen gas

Exercises and Activities

• A solution turns red litmus blue, indicating a pH more than 7
• A solution reacts with crushed eggshells to give a gas that turns lime-water milky, indicating the presence of acid
• A solution of NaOH can be neutralised by HCl, and the amount of HCl required depends on the amount of NaOH
• Antacids are used to treat indigestion
• Acids react with metals to form salts and evolve hydrogen gas
• Compounds like alcohols and glucose contain hydrogen but are not categorised as acids
• Distilled water does not conduct electricity, whereas rainwater does due to the presence of ions
• Acids do not show acidic behaviour in the absence of water
• Universal indicators can be used to test the pH of solutions
• Plaster of Paris should be stored in a moisture-proof container to prevent hydration

Group Activity

• Preparing an indicator using beetroot extract and testing its efficacy with different substances
• Preparing a soda-acid fire extinguisher using sodium hydrogencarbonate and dilute sulphuric acid, and demonstrating its effectiveness in putting out a fire

Test your knowledge of basic chemistry concepts, including chemical reactions and properties of compounds like baking powder and copper sulphate.