Assertion: metal's oxide | /r/HasProperty | colourless crystals
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Source sentences:
text: e.g. sodium chloride NaCl or Na+Cl– These oxides and halides ionic compounds are colourless crystals or white solids, soluble in water to give colourless solutions (usually pH 7 for their salts, pH 13–14 for the oxides because the MOH alkali formed).