Answer:
The first one has the weakest bond
Explanation:
The number of atoms together shows how strong the bonds in the second bond it is 4 bonds, the third is 8 bonds, the 4th one is 4 bonds thus why the first bond is the weakest.
<span>Elements are matter made of one kind of atom.</span>
Explanation:
Molar mass of HBr = 81 g/mol
Molar mass of nitrogen dioxide gas = 46 g/mol
Molar mass of ethane = 30 g/mol
Graham's Law states that the rate of effusion or diffusion of gas is inversely proportional to the square root of the molar mass of the gas. The equation given by this law follows the equation:

So, the gas with least molar mass will effuse out fastest from the container and that is ethane gas.
The formula for average kinetic energy is:

where,
k = Boltzmann’s constant = 
T = temperature = 273.15 K ( at STP)
As we can see from the formula that kinetic energy depends upon only temperature of the gas molecule.
So, from this we can say that all the gas molecules have the same average kinetic energy at this temperature.