This is a homogenous mixture because you cannot differentiate between the members of the mixture. A technique might be heating them until one melts and evaporates due to different boiling temperatures, or mixing them together with fluids that would dissolve one, yet keep the other one whole.
Answer:

Explanation:
Since we have $N_A$ number of molecules in 22.4 L, in 15 L we have:
$\frac{15}{22.4}\times 6.023 \times 10^{23}$ molecules.
The oceanographers define salinity by the number of grams of salt per kilogram of water.
Salinity is illustrated as how much salt is present in the given amount of water. It is dependent upon how much salt is found in the ocean in the specific regions. If there is a sunny environment, it may evaporate an ample amount of water, and leave behind a lot of salt, thus, the water has more salinity.
The salinity of the ocean is usually measured in Practical Salinity Unit (PSU), it is a unit based on the characteristics of seawater conductivity.
<span>The balloons volume as it
rises increases because at higher altitude external pressure is lower, so the
air molecules inside the balloons tends to expand more to attain mechanical
equilibrium, where the external pressure and internal pressure are equal. Unlike
when the balloon is on the ground, external pressure is great so the gas
molecule cannot push the walls of the balloon so it is like underinflated.</span>