Answer:

Explanation:
You calculate the energy required to break all the bonds in the reactants.
Then you subtract the energy needed to break all the bonds in the products.
N₂ + O₂ ⟶ 2NO
N≡N + O=O ⟶ 2O-N=O
Bonds: 2N≡N 1O=O 2N-O + 2N=O
D/kJ·mol⁻¹: 941 495 201 607

Answer:
There are different ways to investigate density. In this required practical activity, it is important to:
record the mass accurately
measure and observe the mass and the volume of the different objects
use appropriate apparatus and methods to measure volume and mass and use that to investigate density
Explanation:
A and c
Because it defines the boundaries of the system