Question 12 Marks
When a piece of limestone reacts with dilute HCl , a gas X is produced. When gas X is passed through lime water then a white precipitate Y is formed. On passing excess of gas X , the white precipitate dissolves forming a soluble compound Z.
a. What are $\mathrm{X}, \mathrm{Y}$ and Z ?
b. Write equations for the reactions which take place :
i. When limestone reacts with dilute HCl .
ii. When gas X reacts with lime water to form white precipitate Y.
a. What are $\mathrm{X}, \mathrm{Y}$ and Z ?
b. Write equations for the reactions which take place :
i. When limestone reacts with dilute HCl .
ii. When gas X reacts with lime water to form white precipitate Y.
Answer
View full question & answer→a. Compound $\mathbf{X}$ is Carbon Dioxide ( $\mathrm{CO}_{2}$ ); Compound $\mathbf{Y}$ is Calcium Carbonate ( $\mathrm{CaCO}_{3}$ ); Compound $\mathbf{Z}$ is Calcium Hydrogen Carbonate $\left[\mathrm{Ca}\left(\mathrm{HCO}_{3}\right)_{2}\right]$.
b. i. $\mathrm{CaCO}_{3}(\mathrm{~s})+2 \mathrm{HCl}(\mathrm{l}) \rightarrow \mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g})$
ii. $\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g}) \rightarrow \mathrm{CaCO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})$
b. i. $\mathrm{CaCO}_{3}(\mathrm{~s})+2 \mathrm{HCl}(\mathrm{l}) \rightarrow \mathrm{CaCl}_{2}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\mathrm{CO}_{2}(\mathrm{~g})$
ii. $\mathrm{Ca}(\mathrm{OH})_{2}(\mathrm{aq})+\mathrm{CO}_{2}(\mathrm{~g}) \rightarrow \mathrm{CaCO}_{3}(\mathrm{~s})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})$