Question

Which of the following has the highest molar mass? \((\text{Atomic masses: N}=14,\ \text{O}=16,\ \text{Ag}=108,\ \text{Pb}=208,\ \text{Na}=23,\ \text{H}=1,\ \text{K}=39)\)

• A. Silver nitrate
• B. Lead nitrate
• C. Ammonium nitrate
• D. Sodium nitrate
• E. Potassium nitrate

Hint:

In molar mass questions, first write the correct formula, especially for compounds containing polyatomic ions such as \( \text{NO}_3^- \). Then multiply carefully by subscripts.

Answer 1

The Correct Option is B

Step 1: Write the chemical formulas of all compounds.
The given compounds are: \[ \text{Silver nitrate} = \text{AgNO}_3 \] \[ \text{Lead nitrate} = \text{Pb(NO}_3\text{)}_2 \] \[ \text{Ammonium nitrate} = \text{NH}_4\text{NO}_3 \] \[ \text{Sodium nitrate} = \text{NaNO}_3 \] \[ \text{Potassium nitrate} = \text{KNO}_3 \]

Step 2: Find the molar mass of silver nitrate.
For \[ \text{AgNO}_3 \] \[ M = 108 + 14 + 3(16) \] \[ =108+14+48=170 \]

Step 3: Find the molar mass of lead nitrate.
For \[ \text{Pb(NO}_3\text{)}_2 \] \[ M = 208 + 2(14 + 3\times16) \] \[ =208 + 2(14+48) \] \[ =208 + 2(62)=208+124=332 \]

Step 4: Find the molar mass of ammonium nitrate.
For \[ \text{NH}_4\text{NO}_3 \] \[ M = 2(14) + 4(1) + 3(16) \] \[ =28+4+48=80 \]

Step 5: Find the molar masses of sodium nitrate and potassium nitrate.
For \[ \text{NaNO}_3 \] \[ M = 23+14+48=85 \] For \[ \text{KNO}_3 \] \[ M = 39+14+48=101 \]

Step 6: Compare all the molar masses.
The values obtained are: \[ \text{AgNO}_3 = 170 \] \[ \text{Pb(NO}_3\text{)}_2 = 332 \] \[ \text{NH}_4\text{NO}_3 = 80 \] \[ \text{NaNO}_3 = 85 \] \[ \text{KNO}_3 = 101 \] The highest among these is \[ 332 \] which corresponds to lead nitrate.

Step 7: Final conclusion.
Hence, the compound having the highest molar mass is \[ \boxed{\text{Lead nitrate}} \] Therefore, the correct option is \[ \boxed{(2)\ \text{Lead nitrate}} \]