Q5 of 16 Page 57

Write the names of the following compounds and deduce their molecular masses.

Na2SO4, K2CO3, CO2, NaOH, MgCl2, AlPO4, NaHCO3

i. Na2SO4 : Sodium Sulphate


Steps for finding the molecular mass:


Molecular mass of Na2SO4 = 2(Atomic mass of Na) + 1(Atomic mass of S) + 4(Atomic mass of O)


Molecular Mass = 2(23) + 1(32) + 4(16)


= 46 + 32 + 64


= 142 g/mol


ii.K2CO3: Potassium Carbonate


Steps for finding the molecular mass:


Molecular mass of K2CO3 = 2× (Atomic mass of K) + 1× (Atomic mass of C) + 3× (Atomic mass of O)


Molecular Mass = 2× (39) + 1× (12) + 3× (16)


= 78 + 12 + 48


= 138 g/mol


iii.CO2:- Carbondioxide


Molecular mass of CO2 = 1× (Atomic mass of C) + 2× (Atomic mass of O)


Molecular Mass = 1× (12) + 2× (16)


= 12 + 32


= 44 g/mol


iv.NaOH:Sodium Hydroxide


Molecular mass of NaOH = 1× (Atomic mass of Na) + 1× (Atomic mass of O) + 1× (Atomic mass of H)


Molecular Mass = 1× (23) + 1× (16) + 1× (1)


= 23 + 16 + 1


= 40 g/mol


v.MgCl2:Magnesium Chloride


Molecular mass of MgCl2 = 1× (Atomic mass of Mg) + 2× (Atomic mass of Cl)


Molecular Mass = 1× (24) + 2× (35.5)


= 24 + 70


= 94 g/mol


vi.AlPO4:-Aluminium Phosphate


Molecular mass of AlPO4 = 1× (Atomic mass of Al) + 1× (Atomic mass of P) + 4× (Atomic mass of O)


Molecular Mass = 1× (27) + 1× (31) + 4× (16)


= 27 + 31 + 64


= 122 g/mol


vii.NaHCO3: Sodium Bicarbonate


Molecular mass of NaHCO3 = 1× (Atomic mass of Na) + 1× (Atomic mass of H) + 1× (Atomic mass of C) + 3× (Atomic mass of O)


Molecular Mass = 1× (23) + 1× (1) + 1× (12) + 3× (16)


= 23 + 1 + 12 + 48


= 84 g/mol


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