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