Question

1. How many moles of HNO3 are contained in 1.0 mL of concentrated nitric acid? Please try to show me your calculations so I can learn how to do it.
2. Draw a lewis electron dot structure for the nitronium ion, NO2+. Show all valence electrons.

Answer 1

1. Concentrated nitric acid is 70% by weight HNO3. The concentration in M is approximately 15.8 M (both of these values can be looked up).

A concentration of 15.8 M means that each liter of this solution contains 15.8 moles of HNO3.

You have 1.0 mL of solution. Since there are 1000 mL in 1 L, you have 1/1000 L nitric acid solution.

Thus, you have 15.8 / 1000 = 0.0158 moles of nitric acid.


2. The nitronium ion has 5 valence electrons for N and 6 each for O. But it is also positively charged, so one electron is missing. Thus, there are 5 + 6 + 6 -1 = 16 electrons total.

We assume the ion is symmetrical, and place the N in the middle. 4 electrons form two single bonds to the O atoms, and then 4 additional electrons from the double bonds. This gives an octet around N. The remaining 8 electrons are split between the two O atoms, given them full octets as well. The positive charge resides on N: