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When testing for a reducing sugar with alkaline copper(II) sulphate, the reducing agent is ( the reducing sugar, starch, copper(II) sulphate, hydrogen ions ). At a temperature of ( 80, 100, 75, 25 ) degrees C, for a duration of ( 3 minutes, 1 minute, 20 seconds, 45 seconds ), ( Cu2+, Cu3+, Cu+ ) is is reduced to ( Cu+, Cu2+, Cu3+, Cu ), by gaining ( an electron, two electrons, a protons ). The new, reduced ion forms ( copper oxide, copper hydroxide, copper(I) sulphate, copper ), which precipitates. The colour change is from ( blue, colourless, white, orange, green ) to ( red, orange, green, blue, colourless ), and the degree of colour change is proportional to the concentration of reducing sugar.