(2) Xiao Yi questioned Xiao Hu's plan after consulting relevant information, and thought that the above plan was not enough to prove that soda contained carbon dioxide. The reason is that citric acid can also turn purple litmus test solution red.
(3) After thinking about it, I think the question of Xiaoyi is reasonable. So I redesigned an experiment with the same principle. I designed an experiment: heating soda water, absorbing carbon dioxide with water, dropping purple litmus test solution, and purple litmus test solution turned red.
(4) I can also use the principle different from the above experiment to design the scheme shown in Table 2, which proves that soda contains carbon dioxide:
Table 2
Experimental steps and methods experimental phenomena experimental conclusions
Heating soda water, absorbing carbon dioxide with limewater to produce precipitate, continuously introducing carbon dioxide, and dissolving the precipitate again.
I can write the chemical equation of the above reaction:
Calcium hydroxide+carbon dioxide = calcium carbonate +H2O
Calcium carbonate+carbon dioxide +H2O = calcium bicarbonate 2