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: Understanding the Concept:
Molar mass is the mass of one mole of a substance. To find the molar mass of a compound, we need to sum the atomic masses of all the atoms present in its chemical formula.
Step 2: Key Formula or Approach:
We will calculate the molar mass for each compound listed using the provided atomic masses.
Step 3: Detailed Explanation:
Let's calculate the molar mass for each option:

(A) Silver nitrate (AgNO\(_3\)):
Molar Mass = (1 \(\times\) Ag) + (1 \(\times\) N) + (3 \(\times\) O)
= (1 \(\times\) 108) + (1 \(\times\) 14) + (3 \(\times\) 16) = 108 + 14 + 48 = 170 g/mol.

(B) Lead nitrate (Pb(NO\(_3\))\(_2\)):
Molar Mass = (1 \(\times\) Pb) + (2 \(\times\) N) + (6 \(\times\) O)
= (1 \(\times\) 208) + (2 \(\times\) 14) + (6 \(\times\) 16) = 208 + 28 + 96 = 332 g/mol.

(C) Ammonium nitrate (NH\(_4\)NO\(_3\)):
Molar Mass = (2 \(\times\) N) + (4 \(\times\) H) + (3 \(\times\) O)
= (2 \(\times\) 14) + (4 \(\times\) 1) + (3 \(\times\) 16) = 28 + 4 + 48 = 80 g/mol.

(D) Sodium nitrate (NaNO\(_3\)):
Molar Mass = (1 \(\times\) Na) + (1 \(\times\) N) + (3 \(\times\) O)
= (1 \(\times\) 23) + (1 \(\times\) 14) + (3 \(\times\) 16) = 23 + 14 + 48 = 85 g/mol.

(E) Potassium nitrate (KNO\(_3\)):
Molar Mass = (1 \(\times\) K) + (1 \(\times\) N) + (3 \(\times\) O)
= (1 \(\times\) 39) + (1 \(\times\) 14) + (3 \(\times\) 16) = 39 + 14 + 48 = 101 g/mol.

Step 4: Final Answer:
Comparing the calculated molar masses:
Silver nitrate: 170 g/mol
Lead nitrate: 332 g/mol
Ammonium nitrate: 80 g/mol
Sodium nitrate: 85 g/mol
Potassium nitrate: 101 g/mol
The highest molar mass belongs to Lead nitrate.