✔ 最佳答案
Cu^2+ is blue colour; SO4^2- is colourless
while sodium is colourless and dichromate ion is orange.
When they mix, the colour will turn to bluish orange (I dont know it's right or not, the colour contains blue with orange)
2010-09-21 21:28:05 補充:
while sodium ion(Na+)
it is not sodium atom, sorry!
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