The formula for mole fraction is:
-(1)
The solubility of oxygen gas = 1.0 mmol/L (given)
1.0 mmol/L means 1.0 mmol are present in 1 L.
Converting mmol to mol:
So, moles of oxygen = 0.001 mol
For moles of water:
1 L of water = 1000 mL of water
Since, the density of water is 1.0 g/mL.
So, the mass of water is 1000 g.
Molar mass of water = 18 g/mol.
Number of moles of water = 
Substituting the values in formula (1):
Hence, the mole fraction is 
.
They are all equal to one mole (all of the above).
Answer:
<u><em>The correct option is C) the moon takes the same time to rotate and revolve.</em></u>
Explanation:
Scientific experiments have concluded that it takes approximately 23 days for the moon to rotate and also it takes the same duration for the moon to revolve around the Earth. Due to this consistency, the moon appears to be still.
<em>Such synchronization results in the same face of the moon to be directed towards the Earth. Hence, the same craters of the moon will be observed by the scientist every day.</em>
<em></em>
Other options, like option D, is not correct because there will be craters on the other side of the moon too. But as we see the same side of the moon, hence we cannot see the craters present on the other side of the moon.
