Question

In \( PO_4^{3-} \), the formal charge on each oxygen atom and the P - O bond order respectively are

• A. -0.75, 0.6
• B. -0.75, 1.0
• C. -0.75, 1.25
• D. -3, 1.25

Hint:

For symmetrical polyatomic ions, formal charge is simply (total charge)/(number of atoms). Bond order is (total valency of central atom)/(number of surrounding atoms) if all surrounding atoms are identical. \

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
A "just sinking" object has an average density equal to the density of the fluid (water). We need to find the ratio of the cavity volume \((V_c)\) to the material volume of the stopper \((V_m)\).

Step 2: Key Formula or Approach:
For an object to just sink, the total weight must equal the buoyancy force: \[ W = B \implies \rho_{\text{avg}} V_{\text{total}} g = \rho_w V_{\text{total}} g \implies \rho_{\text{avg}} = \rho_w \]

Step 3: Detailed Explanation:
Let \( V_c \) be the volume of the cavity and \( V_m \) be the volume of the glass material.
The total volume \( V_t = V_m + V_c \).
The mass of the stopper is purely from the glass material: \( m = \rho_g V_m \).
Given relative density of glass is 2.5, so \( \rho_g = 2.5 \rho_w \).
For "just sinking": \[ \text{Weight of stopper} = \text{Buoyancy force} \] \[ \rho_g V_m g = \rho_w V_t g \] \[ (2.5 \rho_w) V_m = \rho_w (V_m + V_c) \] \[ 2.5 V_m = V_m + V_c \] \[ 1.5 V_m = V_c \] \[ \frac{V_c}{V_m} = \frac{1.5}{1} = \frac{3}{2} \]

Step 4: Final Answer:
The ratio of the volume of the cavity to the material volume of the stopper is \(3:2\).