A. The mass of one mole of the virus is calculated by multiplying the mass of a single virus by the Avogadro's number which is equal to 6.022 x 10^23. Performing this operation,
mass = (9.0 x 10^-12 mg)(6.022 x 10^23) = 5.42 x 10^12 mg
In correct number of significant figures, the answer would only have to be 5.4 x 10^12 mg.
b. The number of moles of the virus that will have the same mass as the oil tanker is calculated by dividing the mass of the oil tanker by the mass of one mole of the virus. Note that doing division, both would have to have the same units.
n = (3.0 x 10^7 kg) / (5.4 x 10^12 mg)(1 g/1000 mg)(1 kg/1000 g)
Simplifying,
n = 6
In correct number of significant figures, the answer is 6.0.
I think this one is the organelles.
We know that there are 100 cm in 1 m, so we can use this to convert to meters:
Therefore we know that 
cm is equal to 2.41 m.
The trajectory of their motion knocked the Earth into a different orbit.
Answer:
ΔE = 73 J
Explanation:
By the first law of thermodynamics, the energy in the system must conserved:
ΔE = Q - W
Where ΔE is the internal energy, Q is the heat flow (positive if it's absorbed by the system, and negative if the system loses heat), and W is the work (positive if the system is expanding, and negative if the system is compressing).
So, Q = + 551 J, and W = + 478 J
ΔE = 551 - 478
ΔE = 73 J
