Q23 of 75 Page 81

In a chemical compound calcium sulphate:

(i) Identify the two ions.


(ii) Write the chemical formula of compound formed when positive ion is replaced by sodium ion.


(iii) Name the resulting compound.

(i) The two ions are Ca2+ (cation) and SO42-(anion)


(ii) When positive ion is replaced by sodium ion:



Chemical formula: Na2SO4


(iii) The name of the resulting compound (Na2SO4) is sodium sulphate.


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21

Write the chemical formulae of Nitrates (NO3–) of Na+, K+, Al3+, Mg2+, Ca2+, Zn2+.

 22

Write the chemical formulae and names of the compounds formed by the following ions:

(i) Cr3+ and SO42–


(ii) Pb2+ and NO3–


(iii) Mg2+ and CO32–

 24

(i) Calculate the formula unit mass of Na2CO3.

[given atomic mass of Na = 23 u, C = 12 u and O = 16 u]


(ii) What is the mass of one mole of oxygen atoms?


(iii) Convert 12g of oxygen gas into mole, if atomic mass of oxygen is 16 u.

 25

An element X has a valency 1.

(i) Write the chemical formula of its phosphide.


(ii) Write the chemical formula of its chloride.


(iii) Is element X a metal or a non-metal?