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प्रश्न
Explain the terms ‘chemical formula’.
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उत्तर १
Chemical formula is a representation of a substance either element or compound by means of symbols.
उत्तर २
Chemical Formula: “A molecule of a substance element or compound could be represented by symbols. Representation known as chemical formula i.e. molecular formula of oxygen gas is O2 water H2O, hydrochloric acid HCl etc.
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संबंधित प्रश्न
Give the symbols and valencies of following radicals:
(a) Hydroxide (b) Chloride
(c) Carbonate (d) ammonium
(e) Nitrate
Write the names of following elements Na, C, Kr, U, Ra, Fe, Co.
Give two examples of the following :
Solid + Solid mixture
Name the elements represented by the following symbols :
Hg, Pb, Au, Ag, Sn
An atom of an element is denoted by a “symbol” Explain the meaning of the term ‘symbol’. State a reason for representing the following element by its symbol.
Copper by ‘Cu’
Match the metallic elements – with their correct symbols Metallic elements
| Metallic elements | Symbol |
| (a) Potassium | (1) Ca |
| (b) Sodium | (2) Zn |
| (c) Calcium | (3) Pb |
| (d) Magnesium | (4) Hg |
| (e) Zinc | (5) Cu |
| (f) Aluminum | (6) Au |
| (g) Iron | (7) K |
| (h) Lead | (8) Fe |
| (i) Copper | (9) Al |
| (j) Mercury | (10) Na |
| (k) Silver | (11) Mg |
| (l) Platinum | (12) Pt |
| (m) Gold | (13) Ag |
Match the formulas of the following gases with their correct names :
Gases - (a) H2 (b) N2 (c) O2 (d) Cl2 (e) HCI (f) NH3 (g) CO (h) CO2 (i) SO2 (j) NO (k) NO2.
Names:
(1) Ammonia (2) Nitrogen Dioxide (3) Oxygen (4) Hydrogen (5) Nitrogen (6) Chlorine (7) Carbon Monoxide (8) Sulphur Dioxide (9) Nitrogen Monoxide (10) Carbon Dioxide (11) Hydrogen Chloride
State which element exists in the highest percentage in human body.
Elements are mainly classified into metals and non-metals. State six properties of metals which differ from non-metals.
Give the symbol of the following element:
Boron
Give the symbol of the following element:
Sodium
State the type of element for the following:
Fluorine
State the type of element for the following:
Iodine
Write the radical of the following valency:
Chlorine [Chloride]
Write the radical of the following valency:
Hydroxide
Write the chemical formula of the following:
Sodium bromide
Certain metal exhibit variable valencies which include valencies: 1+, 2+, 3+, and 4+.
State the variable valency of the following metal.
Silver
write symbol with the variable valency
State whether the following ion or radical given below of a non-metallic element exhibits valency: 1–, 2– or 3–. (write the ion or radical with the correct valency).
Sulphate
Describe the different ways in which we can write the symbols of elements. Give appropriate examples.
