Discussion
Which of the following has the highest molar mass?
(Atomic mass: N=14, O=16, Ag=108, Pb=208, Na=23, H=1, K=39)
Answer: B
The highest molar mass belongs to Lead nitrate, Pb(NO3)2.
Each nitrate group, NO3, weighs 14 + 3 × 16 = 62. Lead is divalent, so its nitrate carries two of them:
\[ \begin{aligned} \mathrm{Pb(NO_{3})_{2}} &= 208 + 2 \times 62 = 332 \\ \mathrm{AgNO_{3}} &= 108 + 62 = 170 \end{aligned} \]
The others are lighter still: potassium nitrate 39 + 62 = 101, sodium nitrate 23 + 62 = 85, and ammonium nitrate NH4NO3 = 18 + 62 = 80. Silver nitrate is the trap, since silver is heavy, but it has only one nitrate group.
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