The answer is "A. a pure substance can be separated by chemical means, while a mixture can be separated by physical means". A pure substance only has one type of substance, whereas a mixture has more than one. A pure substance therefore, can only be separated chemically, because it is not two things mixed together, whereas a mixture can be separated physically because there are multiple substances.
Cells need ribosomes to make protein.
<u>Answer:</u> The mass of gallium produced by the electrolysis is 0.0354 grams.
<u>Explanation:</u>
The equation for the deposition of Ga(s) from Ga(III) solution follows:

- To calculate the total charge, we use the equation:

where,
C = charge
I = current = 0.490 A
t = time required (in seconds) =
(Conversion factor: 1 min = 60 s)
Putting values in above equation, we get:

- To calculate the moles of electrons, we use the equation:

where,
C = charge = 147 C
F = Faradays constant = 96500

- Now, to calculate the moles of gallium, we use the equation:

where,
n = number of electrons transferred = 3
Putting values in above equation, we get:

- To calculate the mass of gallium, we use the equation:

Moles of Gallium = 
Molar mass of Gallium = 69.72 g/mol
Putting values in above equation, we get:

Hence, the mass of gallium produced by the electrolysis is 0.0354 grams.
Density = mass / volume
1.5 = m / 50.0
m = 1.5 x 50.0
m = 75 g
hope this helps!