Advertisements
Advertisements
प्रश्न
Define the term Relative molecular mass. State why indirect methods are utilised to determine the absolute mass of an atom. Explain in brief the indirect method used.
उत्तर
Relative molecular mass [RMM] of an element/compound : “Is the number of times one molecule of the substance is heavier than 1/12 the mass of an atom of carbon [C12].
RAM = `"Mass of one atom of the element"/("Mass of one atom of carbon"["C"^12])`
OR
“Mass of one molecule as compared with the 1/12 mass of an atom of carbon[C12]”
RMM = `("Mass of one molecule of the substance")/((1/2) "Mass of one atom of carbon"["C"^12])`
To determine the absolute mass of an atom indirect methods are utilised as Atom are extremely small and very light.
An isotope of carbon C12 [carbon -12 atom] has been assigned an atomic mass of exactly 12 atomic mass units] is used.
APPEARS IN
संबंधित प्रश्न
Write the chemical formula of the Calcium oxide.
Write down the formulae for the following compounds :
Magnesium hydroxide
An element B shows valencies of 4 and 6. Write the formulae of its two oxides.
Write chemical formula of the sulphate of Aluminium, Ammonium and Zinc.
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 |
Name the element in the compound and give the formula of the following compound:
Blue vitriol
Write the formula of the following compound:
Sodium chloride
Write the formula of the following compound:
Sodium permanganate
Write the formula of the following compound:
Sodium sulphate
Write the formula of the following compound:
Sodium iodide
Write the formula of the following compound:
Calcium carbonate
Write the formula of the following compound:
Calcium bisulphite
Write the formula of the following compound:
Magnesium chloride
Write the formula of the following compound:
Iron [II] sulphide
Write the formula of the following compound:
Lead [II] nitrate
What do you understand by chemical formula of a compound? What is its significance?
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.
