Answer:
6.25 grams is the mass of solute dissolved.
Explanation:
w/w % : The percentage mass or fraction of mass of the of solute present in total mass of the solution.

Mass of the solution = 50.0 g
Mass of the solvent = x
w/w % = 12.5%

x = 6.25 g
6.25 grams is the mass of solute dissolved.
Answer:
The new volume of the gas remains the same. That is new volume of gas is 1.33 litres
Explanation:
This is because gases do not have a definite shape. They therefore take the shape of their containing vessels and hence their volumes are determined by the volume of the container.
For the question above even if some of the gas escapes, as long as there is gas present in the container, its volume remains the same, that is occupies the same space in the container
Student B because it requires a hypothesis
Nails are made up of iron not of phosphorus and barium.
As both phosphorous and barium are relatively weaker than iron ,phosphorus breaks easily and barium is also fairly weak. Iron nails are already also not that strong, but their weight and strength are sufficient.
So the nails are made up of iron.