Question

When ${\mathrm{CO}}_2$ is passed through lime water, milkiness formed is due to:

• A. ${\mathrm{CaCO}}_3$
• B. $\mathrm{Ca}{\left(\mathrm{OH}\right)}_2$
• C. $\mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2$
• D. $\mathrm{None}\mathrm{of}\mathrm{these}$

Answer 1

The correct option is A

${\mathrm{CaCO}}_3$

The explanation for the correct option:

(A) ${\mathrm{CaCO}}_3$

Lime water is calcium hydroxide that, when exposed to carbon dioxide, turns milky due to the production of calcium carbonate(${\mathrm{CaCO}}_3$).

Reactions

$\mathrm{Ca}{\left(\mathrm{OH}\right)}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(\mathrm{g}\right)\to {\mathrm{CaCO}}_3\left(\mathrm{ppt}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

The explanation for the incorrect options:

Option (B)

when (${\mathrm{CO}}_2$) is passed through lime water calcium carbonate is formed, not calcium hydroxide

Option (C)

$\mathrm{Ca}{\left({\mathrm{HCO}}_3\right)}_2$ is formed when (${\mathrm{CaCO}}_3$) reacts with both water and carbon dioxide.

Hence, option (A) is correct.