The reaction of h2 with f2 produces hf with δh = –269 kj/mol of hf. if the h–h and h–f bond energies are 432 and 565 kj/mol, respectively, what is the f–f bond energy?

The bond energy of F–F = 429 kJ/mol

Explanation:

Given:

The bond energy of H–H = 432 kJ/mol

The bond energy of H–F = 565 kJ/mol

The bond energy of F–F = ?

Given that the standard enthalpy of the reaction:

H₂ (g) + F₂ (g) ⇒ 2HF (g)

ΔH = –269 kJ/mol

So,

ΔH = Bond energy of reactants - Bond energy of products.

–269 kJ/mol = [1. (H–H) + 1. (F–F)]  - [2. (H–F)]

Applying the values as:

–269 kJ/mol = [1. (432 kJ/mol) + 1. (F–F)]  - [2. (565 kJ/mol)]

Solving for , The bond energy of F–F , we get:

The bond energy of F–F = 429 kJ/mol

close lines strong magnet less close weaker

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.