Chlorine is prepared commercially by the electrolysis of sodium chloride. If molten sodium chloride is places in an electrolytic device and the power source is turned on, the negatively charged chlorine ions Cl- move toward the positively charged electrode. A container can be placed above the anode (the positively charged electrode) to collect the chlorine gas produced by the reaction.
2NaCl --> 2Na + Cl2
In the lab preparation of chlorine, manganese dioxide is heated with concentrated hydrochloric acid HCl. A redox reaction takes place in which manganese chloride, water and chlorine are produced.
4HCl + MnO2 --> MnCl2 + 2H2O + Cl2
Chlorine gas can be tested for with moist blue litmus paper which will turn red in the presence of chlorine gas.
Prentice Hall Chemistry
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