Question

If you could drop 12 atoms of copper onto a beaker containing nitric acid, how many molecules of NO would be produced?

A) 12
B)8
C)4
D)2

Answer 1

B) 8.0 molecules.

Step-by-step explanation:

• From the balanced equation: 3Cu + 8HNO₃ → 3Cu(NO₃)₂ + 2NO + 4H₂O,

It is clear that 3.0 atoms of Cu react with 8.0 molecules of HNO₃ to produce 3.0 molecules of Cu(NO₃)₂, 2.0 molecules of NO, and 4.0 atoms of H₂O.

Note that: The no. of atoms and molecules is the same ratio to the no. of moles.

Using cross multiplication:

3.0 atoms of Cu produce → 2.0 molecules of NO, from the balanced equation.

12.0 atoms of Cu produce → ??? molecules of NO.

∴ The no. of molecules of NO produced = (2.0 molecules)(12.0 atoms)/(3.0 atoms) = 8.0 molecules.