The following statements are made in connection with carbon dioxide...

$I$. Carbon dioxide is prepared by burning carbon (or) by the reaction of a carbonate and an acid (or) by decomposition of lime stone.

${CaCO}_{3} + 2HCl \to {CaCl}_{2} + {H}_{2}O + {CO}_{2}$

${CaCO}_{3}\overset{∆}{→}CaO + {CO}_{2}$

$II$. Samples of~carbon dioxide~contain carbon and oxygen in the mass~ratio& of& $3: 8$

$\mathop{C}_{123} + \mathop{O₂}_{328} \to {CO}_{2}$

$III$.~ When carbon dioxide is continuously bubbled through lime water, initially due to the formation of insoluble calcium carbonate~lime water turns milky and then again when reacted with excess carbon dioxide due to soluble calcium bicarbonate it becomes~colourless.

$Ca{( OH )}_{2} + {CO}_{2} \to \mathop{CaCO₃}_{white precipitate}{CaCO}_{3} + {H}_{2}O + \mathop{{CO}_{2}}_{excess } ⟶ \mathop{Ca{( {HCO}_{3} )}_{2}}_{water soluble}$