Answer:
a) The number density is 3.623 × 10⁻³ 
The mass of the atmosphere is 1.3 × 10²²Kg
b) The pressure is 10⁻²⁰ Millimeter of mercury
c) The mass mixing ratio is 0.0107
The partial pressure of ethane is 0.01114 Pa
Yes it is condensable because it boiling point is -88.5 C which is equivalent to 184.5 K i.e is adding 273 to -88.5C and the temperature of the atmosphere is 37 K.
Explanation:
The explanation is on the first and second uploaded image
I believe so not 100% sure but i am about 50% sure
mass of iron block given as

density of iron block is

now the volume of the iron piece is given as


Now when this iron block is complete submerged in oil inside the beaker the buoyancy force on the iron block will be given as

here we know that
= density of liquid = 916 kg/m^3


Now for the reading of spring balance we can say the spring force and buoyancy force on the block will counter balance the weight of the block at equilibrium



So reading of spring balance will be 16.45 N
Now for other scale which will read the normal force of the surface we can write that normal force on the container will balance weight of liquid + container and buoyancy force on block



So the other scale will read 36.47 N