Question

2 ml of HCl was taken in each of the three test tubes A, B and C to which 2 gm of limestone was added. The gas liberated from each of them were passed through limewater, water and hydrochloric acid respectively. Which of the test tube(s) will give a milky solution?

• A. A
• B. B
• C. Both A and B
• D. All three test tubes.

Answer 1

The correct option is A A

The addition of limestone $\left(CaC{O}_3\right)$ in hydrochloric acid $\left(HCl\right)$ results in the formation of carbon dioxide, which when passed through limewater $\left(Ca\right(OH{)}_2)$ gives a milky solution. The reaction below will be occuring in all three test tubes.

${\mathrm{CaCO}}_3\left(s\right)+2\mathrm{HCl}\left(\mathrm{aq}\right)\to {\mathrm{CaCl}}_2\left(\mathrm{aq}\right)+{\mathrm{CO}}_2\left(g\right)+H_{2}O\left(l\right)$

However, the solution in test tube A only turns milky white due to the formation of calcium carbonate as shown below.

$\mathrm{Ca}\left(\mathrm{OH}{)}_2\right(\mathrm{aq})+{\mathrm{CO}}_2(g)\to {\mathrm{CaCO}}_{3^{}}(s)+H_{2^{}}O(l)\mathrm{milky}\mathrm{solution}$

$C{O}_2$ neither turns water nor $HCl$ milky white.