# Calculate the relative molecular weight and formula of substances: a) CH4 NH3 H2O

Calculate the relative molecular weight and formula of substances: a) CH4 NH3 H2O b) CO2 NO2 N2O5 NO c) SO2 SO3 SiO2 P2O5

a) Mr (CH4) = Ar (C) + 4 * Ar (H) = 12 + 4 = 16;

Mr (NH3) = Ar (N) + 3 * Ar (H) = 14 + 3 = 17;

Mr (H2O) = 2 * Ar (H) + Ar (O) = 2 + 16 = 18;

b) Mr (CO2) = Ar (C) + 2 * Ar (O) = 12 + 32 = 44;

Mr (NO2) = Ar (N) + 2 * Ar (O) = 14 + 32 = 46;

Mr (N2O5) = 2 * Ar (N) + 5 * Ar (O) = 28 + 80 = 108;

Mr (NO) = Ar (N) + Ar (O) = 14 + 16 = 30;

c) Mr (SO2) = Ar (S) + 2 * Ar (O) = 32 + 32 = 64;

Mr (SO3) = Ar (S) + 2 * Ar (O) = 32 + 48 = 80;

Mr (SiO2) = Ar (Si) + 2 * Ar (O) = 28 + 32 = 60;

Mr (P2O5) = 2 * Ar (P) + 5 * Ar (O) = 62 + 80 = 142.

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