Chemical symbols are the brief notation used by chemists to express the full and lengthy names of the elements. Similarly, the chemical formula is the brief representation of a chemical compound. The chemical formula tells us the actual number of atoms of the elements present in one molecule of the compound. The formula of the compound is written from the knowledge of the valencies of the radicals (or elements) forming the compound.
Answer the following questions after reading the passage.
(1) Write symbols of two elements whose symbols contain the 2nd alphabet of the English language.
(2) Write the formula of oxalate of calcium.
(3) Write the name and symbol of the element whose symbol contains the first and third letter of its name.
(4) How many compounds from the following list have an equal number of atoms in their molecules/ formula units?
Iron (II) sulfate, aluminum sulfate, iron (III) sulfate, barium nitrate, chromium oxalate, magnesium carbonate
(a) 3 (b) 5 (c) 4 (d) 2

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Solution

(1) 2nd alphabet of the English language is B
The symbols of two elements whose symbols contain the 2nd alphabet of the English language are Boron(B) and Bismuth(Bi)
(2) The formula for oxalate ion is $C_{2} O_{4}^{2 -}$
Therefore, The formula of oxalate of calcium(Ca) is $Ca (C_{2} O_{4})$ .
(3) The name and symbol of the element whose symbol contains the first and third letter of its name are Magnesium and Mg.
The symbol of Magnesium contains M the first letter of Magnesium and G the third letter of Magnesium.
(4)From the following compound list Iron (II) sulfate and aluminum sulfate both have an equal number of atoms in their molecules/ formula units.
The number of atoms in the molecules/ formula units of Iron (II) sulfate and aluminum sulfate is 17.
It is calculated as the sum of a number of individual atoms in the molecules.
Number of atoms in the molecule of Iron (II) sulfate(Fe₂(SO₄)₃)= 2+3+12
= 17
Number of atoms in the molecule of Iron (II) sulfate(Al₂(SO₄)₃)= 2+3+12
= 17
Number of atoms in the molecule of barium nitrate (Ba(NO₃)₂)= 1+2+6
= 9
Number of atoms in the molecule of chromium oxalate(Cr(C₂O₄))= 1+2+4
= 7
Number of atoms in the molecule of magnesium carbonate(Mg(CO₃))= 1+1+3
= 5
So, The number of atoms in the molecules/ formula units of Iron (II) sulfate and aluminum sulfate is 17.

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