Freeze drying<span> (or lyophilization) removes water from the ice cream by lowering the </span>air pressure<span> to a point where ice sublimates from a </span>solid<span> to a </span>gas<span>. The ice cream is placed in a </span>vacuum chamber<span> and frozen until the water </span>crystallizes<span>. The air pressure is lowered, creating a partial vacuum, forcing air out of the chamber; next heat is applied, </span>sublimating<span> the ice; finally a freezing coil traps the vaporized water. This process continues for hours, resulting in a freeze-dried ice cream slice. </span>
Answer:
B.3/5p
Explanation:
For this question, we have to remember <u>"Dalton's Law of Partial Pressures"</u>. This law says that the pressure of the mixture would be equal to the sum of the partial pressure of each gas.
Additionally, we have a <em>proportional relationship between moles and pressure</em>. In other words, more moles indicate more pressure and vice-versa.
Where:
=Partial pressure
=Total pressure
=mole fraction
With this in mind, we can work with the moles of each compound if we want to analyze the pressure. With the molar mass of each compound we can calculate the moles:
<u>moles of hydrogen gas</u>
The molar mass of hydrogen gas (
) is 2 g/mol, so:
<u>moles of oxygen gas</u>
The molar mass of oxygen gas (
) is 32 g/mol, so:
Now, total moles are:
Total moles = 2 + 3 = 5
With this value, we can write the partial pressure expression for each gas:
So, the answer would be <u>3/5P</u>.
I hope it helps!
This is a straightforward question related to the surface energy of the droplet.
<span>You know the surface area of a sphere is 4π r² and its volume is (4/3) π r³. </span>
<span>With a diameter of 1.4 mm you have an original droplet with a radius of 0.7 mm so the surface area is roughly 6.16 mm² (0.00000616 m²) and the volume is roughly 1.438 mm³. </span>
<span>The total surface energy of the original droplet is 0.00000616 * 72 ~ 0.00044 mJ </span>
<span>The five smaller droplets need to have the same volume as the original. Therefore </span>
<span>5 V = 1.438 mm³ so the volume of one of the smaller spheres is 1.438/5 = 0.287 mm³. </span>
<span>Since this smaller volume still has the volume (4/3) π r³ then r = cube_root(0.287/(4/3) π) = cube_root(4.39) = 0.4 mm. </span>
<span>Each of the smaller droplets has a surface area of 4π r² = 2 mm² or 0.0000002 m². </span>
<span>The surface energy of the 5 smaller droplets is then 5 * 0.000002 * 72.0 = 0.00072 mJ </span>
<span>From this radius the surface energy of all smaller droplets is 0.00072 and the difference in energy is 0.00072- 0.00044 mJ = 0.00028 mJ. </span>
<span>Therefore you need roughly 0.00028 mJ or 0.28 µJ of energy to change a spherical droplet of water of diameter 1.4 mm into 5 identical smaller droplets. </span>
Answer:
here it is
....................................................................................................................................
