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प्रश्न
What is a chemical formula? What is the significance of a formula?give an example to illustrate?
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उत्तर
The chemical formula is used to describe the types of atoms and its number in an element or compound.
Significance- Chemical formula is very important when trying to find information about chemical compounds because they tell us about the elements present and the number of atoms in that compound.
Example - Salt - NaCl, ethanol C2H6O because the molecule of ethanol contains two Carbon, 6 Hydrogen and 1 Oxygen atom.
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संबंधित प्रश्न
What is meant by the symbol of an element ? Explain with examples.
What is the difference between 2H and H2 ?
Write down the formulae for the following compounds :
Calcium oxide
Define ‘formula unit’ of an ionic compound. What is the formula unit of (i) sodium chloride, and
(ii) magnesium chloride ?
Correct the following statement:
Molecular formula of water is H2O2
Give the empirical formula of Acetylene C2H2
Match the following:
| Column A | Column B |
| (a) Pb(NO3)2 | (i) rotten eggs smell |
| (b) CO2 | (ii) burns with a pop sound |
| (c) (NH4)2Cr2O7 | (iii) the suffocating smell of sulphur |
| (d) HCI | (iv) lime water turns milky |
| (e) NO2 | (v) crackling sound |
| (f) O2 | (vi) residue swells up |
| (g) H2 | (vii) brown gas |
| (i) H2S | (viii) supports combustion |
| (j) SO2 | (ix) fumes with NH3 solution |
XCl2 is the chloride of a metal X. State the formula of the sulphate and the hydroxide of the metal X.
Name the element in the compound and give the formula of the following compound:
Green vitriol
Name the element in the compound and give the formula of the following compound:
Glauber’s salt
Write the formula of the following compound:
Sodium aluminate
Write the formula of the following compound:
Sodium hydroxide
Write the formula of the following compound:
Calcium sulphate
Write the formula of the following compound:
Aluminium hydroxide
Write the formula of the following compound:
Copper [II] sulphide
Write the formula of the following compound:
Copper [II] sulphate
Write the chemical formula for the following compounds
- Aluminium sulphate
- Silver nitrate
- Magnesium oxide
- Barium chloride
Which of the following represents a correct chemical formula? Name it.
BiPO4
Complete the following crossword puzzle (Fig. 3.1) by using the name of the chemical elements. Use the data given in Table.
| Across | Down | ||
| 2 | The element used by Rutherford during his α–scattering experiment | 1 | A white lustrous metal used for making ornaments and which tends to get tarnished black in the presence of moist air |
| 3 | An element which forms rust on exposure to moist air | 4 | Both brass and bronze are alloys of the element |
| 5 | A very reactive non–metal stored under water | 6 | The metal which exists in the liquid state at room temperature |
| 6 | Zinc metal when treated with dilute hydrochloric acid produces a gas of this element which when tested with burning splinter produces a pop sound. | 8 | An element with symbol Pb |
