Answer : The mass of sample is, 267.5 grams.
Explanation :
Density : It is defined as the mass of a substance contained per unit volume.
Formula used :

Given:
Volume of Pb = 
Density of Pb = 
Now put all the given values in the above formula, we get the mass of Pb.


Therefore, the mass of sample is, 267.5 grams.
I'm not sure if this is what you're looking for, but I suppose you would have to have the solute and the solution to balance the reaction.
<u>Answer:</u> The final volume of the gas comes out to be 4 L.
<u>Explanation:</u>
To calculate the volume with changing pressure, we use the equation given by Boyle's law.
This law states that pressure is inversely proportional to the volume of the gas at constant temperature and number of moles.
Mathematically,
(At constant temperature and number of moles)
The equation given by this law is:

where,
are initial pressure and volume.
are final pressure and volume.
We are given:

Putting values in above equation, we get:

Hence, the final volume of the gas will be 4 L.
They mimicked the flight of birds.