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प्रश्न
Fill the following blanks with suitable words :
In a chemical reaction, the sum of the masses of the reactants and the products remains unchanged. This is called ....................
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उत्तर
In a chemical reaction, the sum of masses of the reactants and their products remain unchanged. This is called the law of conservation of mass.
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संबंधित प्रश्न
What is meant by a chemical formula ? Write the formulae of one element and one compound.
Write down the formulae for the following compounds :
Calcium oxide
An element Z has a valency of 3. What is the formula of oxide of Z ?
Give the formula and valency of:
aluminium ………………. .
Write the formula of the following compound:
Sodium sulphate
Write the formula of the following compound:
Sodium aluminate
Write the formula of the following compound:
Magnesium bicarbonate
State of the following formula of a compound is incorrect. Incorrectly write the correct formula.
NaClO
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 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.
