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Rules for Net Ionic Equations

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Rule 1 Binary Acids: HCl, HBr, and HI are strong: all other binary acids and HCN are weak. Strong acids are written in ionic form; weak acids are written in molecular form.
Rule 2 Ternary Acids: If the number of oxygen atoms in to inorganic acid molecule exceeds the number of hydrogen atoms by two or more, the acid is strong. We will consider all organic carboxylic acids as weak.

Strong: HClO3, HClO4, H2SO4, HNO3, H2SeO4
Weak: HClO, H3AsO4, H2CO3, H4SiO4, HNO2
Rule 3 Polyprotic Acids: In the second and subsequent ionizations the acids are always weak, whether or not the original is strong or weak.
Rule 4 Bases: Hydroxides of Group 1 and 2 elements except beryllium are strong bases. All others including ammonia, hydroxlamine, and organic bases are weak.
Rule 5 Salts: Salts are written in ionic form if soluble, and in undissociated form if insoluble. Know the solubility rules.
Rule 6 Oxides: Oxides are always written in molecular or undissociated form.
Rule 7 Gases: Gases are always written in molecular form.

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