Advertisements
Advertisements
प्रश्न
What is a chemical formula? What is the significance of a formula?give an example to illustrate?
Advertisements
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.
APPEARS IN
संबंधित प्रश्न
What is meant by the symbol of an element ? Explain with examples.
An element Z has a valency of 3. What is the formula of oxide of Z ?
An element X has a valency of 4 whereas another element Y has a valency of 1. What will be the formula of the compound formed between X and Y ?
The formula of carbonate of a metal M is M2CO3.
What will be the formula of its iodide ?
Fill in the blank:
Formula of iron (ill) carbonate is _____ .
The formula of the nitride of a metal X is XN, state the formula of :
- its sulphate
- its hydroxide.
Write the formula of the following compound:
Potassium zincate
Write the formula of the following compound:
Potassium plumbite
Write the formula of the following compound:
Magnesium carbonate
Write the formula of the following compound:
Aluminium sulphate
Write the formula of the following compound:
Iron [II] chloride
Write the formula of the following compound:
Iron [II] hydroxide
State of the following formula of a compound is incorrect. Incorrectly write the correct formula.
(NH4)3SO4
State of the following formula of a compound is incorrect. Incorrectly write the correct formula.
NaCO3
State of the following formula of a compound is incorrect. Incorrectly write the correct formula.
KNO3
What do you understand by chemical formula of a compound? What is its significance?
Write the molecular formulae for the following compounds
Copper (II) bromide
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 |
Play a game for writing formula.
Example 1: Make placards with symbols and valencies of the elements separately. Each student should hold two placards, one with the symbol in the right hand and the other with the valency in the left hand. Keeping the symbols in place, students should criss-cross their valencies to form the formula of a compound.
Play a game for writing formula.
Example 2: A low-cost model for writing formulae: Take empty blister packs of medicines. Cut them in groups according to the valency of the element, as shown in the figure. Now, you can make formulae by fixing one type of ion into other.
For example:
The formula for sodium sulphate:
2 sodium ions can be fixed on one sulphate ion.
Hence, the formula will be Na2SO4.
Do it yourself:
Now, write the formula of sodium phosphate.
