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CaO

Ar(Ca) = 40

Ar(O) = 16

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Mr(CaO) = 40 + 16 = 56

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w(Ca) = 40/56 = 0,7143 (71,43%)

w(O) = 16/56 = 0,2857 (28,57%)

CO2

Ar(C) = 12

Ar(O) = 16

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Mr(CO2) = 12 + 2×16 = 44

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w(C) = 12/44 = 0,2727 (27,27%)

w(O2) = 2×16/44 = 0,7273 (72,73%)

NaOH

Ar(Na) = 23

Ar(O) = 16

Ar(H) = 1

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Mr(NaOH) = 23 + 16 + 1 = 40

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w(Na) = 23/40 = 0,575 (57,5%)

w(O) = 16/40 = 0,4 (40%)

w(H) = 1/40 = 0,025 (2,5%)

Ca3(PO4)2

Ar(Ca) = 40

Ar(P) = 31

Ar(O) = 16

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Mr(Ca3(PO4)2) = 3×40 + 2×31 + 8×16 = 310

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w(Ca) = 3×40/310 = 0,387 (38,7%)

w(P) = 2×31/310 = 0,2 (20%)

w(O) = 8×16/310 = 0,413 (41,3%)