Question

X, Y, Z are calcium compounds. X is a primary raw material for manufacturing cement. Y is used to recover ammonia in Solvay process and Z is employed for making casts of statues. Identify the incorrect statement from the following:

• A. Y is prepared by adding water to X
• B. Y is also used as a starting material to manufacture bleaching powder
• C. Z is formed by heating gypsum at 373 K
• D. X with P$_4$O$_{10}$ forms calcium phosphate

Hint:

CaCO$_3$ $\xrightarrow{\Delta}$ CaO $\xrightarrow{H_2O}$ Ca(OH)$_2$ is the correct sequence.

Answer 1

The Correct Option is A

Step 1: Read the clues for X, Y, Z.
X is a main raw material for cement, Y is used to recover ammonia in the Solvay process, and Z is used to make casts of statues. All three are calcium compounds, so we match each clue to the right one.

Step 2: Identify X.
The chief raw material for cement is limestone, which is calcium carbonate. So $X = CaCO_3$.

Step 3: Identify Y.
In the Solvay process, slaked lime is used to free ammonia from ammonium chloride. So $Y = Ca(OH)_2$, calcium hydroxide.

Step 4: Identify Z.
The material for casts of statues is plaster of Paris. So $Z = CaSO_4 \cdot \tfrac{1}{2}H_2O$.

Step 5: Test the statement about how Y is made.
One choice says Y is prepared by adding water to X. But adding water to $CaCO_3$ does not give $Ca(OH)_2$. In reality, $Ca(OH)_2$ is made by adding water to quicklime $CaO$, not to limestone. So this statement is wrong.

Step 6: Confirm the incorrect statement.
The other statements about bleaching powder, plaster of Paris from gypsum, and reaction with $P_4O_{10}$ are all correct. Hence the incorrect one is that Y is prepared by adding water to X.
\[ \boxed{\text{Y is prepared by adding water to X}} \]