Indicators tell us whether a substance is acidic or basic by change in colour. There are some substances whose odour changes in acidic or basic media. These are called olfactory indicators.
CHEMICAL PROPERTIES OF ACIDS
CHEMICAL PROPERTIES OF BASES
REACTION OF ACIDS AND BASES WITH METALS
Reaction of acids with metals
the metal in the above reactions displaces hydrogen from the acids. This is seen as hydrogen gas. The metal combines with the remaining part of the acid and forms a compound called a salt. Thus,the reaction of a metal with an acid can be summarised as –
Acid + Metal → Salt + Hydrogen gas
Reaction of base with metal
Reaction of Metal carbonates and Metal Hydrogencarbonates with Acids
Reaction of Acids and Bases with each other
Reaction of Metallic Oxides with Acids
Acid or Base in a Water Solution
Bases generate hydroxide (OH–) ions in water. Bases which are soluble in water are called alkalis pH
A scale for measuring hydrogen ion concentration in a solution, called pH scale has been developed. The p in pH stands for ‘potenz’ in German,meaning power.
When electricity is passed through an aqueous solution of sodium
chloride (called brine), it decomposes to form sodium hydroxide. The
process is called the chlor-alkali process because of the products formed–
chlor for chlorine and alkali for sodium hydroxide.
2NaCl(aq) + 2H2O(l) →2NaOH(aq) + Cl2(g) + H2(g
Bleaching powder is produced by the action of chlorine on dry slaked lime [Ca(OH)2]. Bleaching powder is represented as CaOCl2
Ca(OH)2 + Cl2 →CaOCl2 + H2O
The chemical name of the compound is sodium hydrogencarbonate (NaHCO3). It is produced using sodium chloride as one of the raw materials.
NaCl + H2O + CO2 + NH3—à NH4Cl + NaHCO3
Another chemical that can be obtained from sodium chloride is
Na2CO3.10H2O (washing soda). Sodium carbonate can be obtained by heating baking soda; recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.
Water of crystallisation
is the fixed number of water molecules present in one formula unit of a salt. Five water molecules are present in one formula unit of copper sulphate. Chemical formula for hydrated copper sulphate is CuSO4.5H2O. Similarly the molecule of Na2CO3.10H2O is wet.
One other salt, which possesses water of crystallisation is gypsum.
It has two water molecules as water of cyrstallisation. It has the formula CaSO4.2H2O. On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate
CBSE 10th Standard Science
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CBSE 10th Standard Science Syllabus and Revision Notes
- Class 10 Chapter 1 – Chemical Reactions and Equations
- Class 10 chapter 2 – Acids, Bases and Salts
- Class 10 Chapter 3 – Metals and Non Metals
- Class 10 Chapter 4 – Carbon and its Compounds
- Class 10 Chapter 5 – Periodic Classification of Elements
- Class 10 Chapter 6 – Life Processes
- class 10 chapter 7 – Control and Coordination
- Class 10 Chapter 8 – How do Organisms Reproduce?
- Class 10 Chapter 9 – Heredity and Evolution
- Class 10 Chapter 10 – Light – Reflection and Refraction
- Class 10 Chapter 11 – The Human Eye and the Colourful World
- Class 10 Chapter 12 – Electricity
- Class 10 Chapter 13 – Magnetic Effects of Electric Current
- Class 10 Chapter 14 – Sources of Energy
- Class 10 Chapter 15 – Our Environment
- Class 10 Chapter 16 – Management of Natural Resources