Chemistry
Calculate the relative molecular masses of :
(a) Ammonium chloroplatinate [(NH4)2PtCl6]
(b) Potassium chlorate [KClO3]
(c) CuSO4.5H2O
(d) (NH4)2SO4
(e) CH3COONa
(f) CHCl3
(g) (NH4)2Cr2O7
Mole Concept
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Answer
(a) (NH4)2PtCl6
= (2N) + (8H) + (Pt) + (6Cl)
= (2 x 14) + (8 x 1) + 195 + (6 x 35.5)
= 28 + 8 + 195 + 213
= 444 a.m.u.
(b) KClO3
= (K) + (Cl) + (3O)
= 39 + 35.5 + (3 x 16)
= 39 + 35.5 + 48
= 122.5 a.m.u.
(c) CuSO4.5H2O
= (Cu) + (S) + (4O) + 5(2H + O)
= 63.5 + 32 + (4 x 16) + 5[(2 x 1) + 16]
= 63.5 + 32 + 64 + (5 x 18)
= 63.5 + 32 + 64 + 90
= 249.5 a.m.u.
(d) (NH4)2SO4
= (2N) + (8H) + (S) + (4O)
= (2 x 14) + (8 x 1) + 32 + (4 x 16)
= 28 + 8 + 32 + 64
= 132 a.m.u.
(e) CH3COONa
= (C) + (3H) + (C) + (2O) + (Na)
= 12 + (3 x 1) + 12 + (2 x 16) + 23
= 12 + 3 + 12 + 32 + 23
= 82 a.m.u.
(f) CHCl3
= (C) + (H) + (3Cl)
= 12 + 1 + (3 x 35.5)
= 12 + 1 + 106.5
= 119.5 a.m.u.
(g) (NH4)2Cr2O7
= (2N) + (8H) + (2Cr) + (7O)
= (2 x 14) + (8 x 1) + (2 x 51.9) + (7 x 16)
= 28 + 8 + 103.8 + 112
= 251.8 ≈ 252 a.m.u.
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