Only strontium hydroxide ( Sr(OH) 2) and barium hydroxides ( Ba(OH) 2) are completely soluble from alkaline earth metals. A compound which released a reddish brown gas on reaction with concentrated sulphuric acid and copper turning. in water sodium hydroxide is a base, and it dissolves in water so it is also an alkali Question Alkali earth metals. Definition of ALKALI: In chemistry, an alkali is a basic, ionic salt of an alkali metal or alkaline earth metal element. Copper(I) hydroxide is the hydroxide of the metal copper with the chemical formula of CuOH. D. Copper nitrate Reason 3 : [ actually this is the first reason ] Because it was originally classified as a " Base " ( Metal oxides and Metal hydroxides are originally classified as a " Base " or Alkali ) . them. Some forms of copper(II) hydroxide are sold as "stabilized" copper(II) hydroxide, although they likely consist of a mixture of copper(II) carbonate and hydroxide. A. 2. Because Copper (II) hydroxide will perform as a Base when reacts with acids . Copper(II) hydroxide is the hydroxide of copper with the chemical formula of Cu(OH) 2.It is a pale greenish blue or bluish green solid. It is extremely easily oxidized even at room temperature. Ammonium sulphate. A compound which on heating with sodium hydroxide produces a gas which forms dense white fumes with hydrogen chloride. Bases are usually: metal oxides, such as copper oxide; metal hydroxides, such as sodium hydroxide, or; metal carbonates, such as calcium carbonate It is a mild, highly unstable alkali.The color of pure CuOH is yellow or orange-yellow, but it usually appears rather dark red because of impurities. Cupric hydroxide is a weak base. Copper(I) hydroxide is the hydroxide of the metal copper with the chemical formula of CuOH. copper oxide is a base, but it is not an alkali because it is insoluble. It is a mild, highly unstable alkali.The color of pure CuOH is yellow or orange-yellow,  but it usually appears rather dark red because of impurities. According to this definition , Cu(OH)2 is not an alkali. It is extremely easily oxidized even at room temperature. Some authors also define an alkali as a base that dissolves in water. It is prepared by adding just sufficient aqueous ammonia to cupric sulphate to hold the copper in solution and then precipitating the hydroxide either by the addition of an equivalent quantity of alkali by removing ammonia from the solution using a dessicator. Berrylium hydroxide ( Be(OH) 2) and magnesium hydroxide ( Mg(OH) 2) are completely insoluble in water. 4.