<u>Answer:</u> The partial pressure of oxygen is 160 mmHg
<u>Explanation:</u>
We are given:
Percent of oxygen in air = 21 %
Mole fraction of oxygen in air = 
To calculate the partial pressure of oxygen, we use the equation given by Raoult's law, which is:

where,
= partial pressure of oxygen = ?
= total pressure of air = 760 mmHg
= mole fraction of oxygen = 0.21
Putting values in above equation, we get:

Hence, the partial pressure of oxygen is 160 mmHg
<span>Molarity is expressed as
the number of moles of solute per volume of the solution. We calculate as follows:
2.80 g ( 1 mol / 56.11 g ) = 0.05 mol KOH
Molarity = 0.05 mol KOH / 750 mL ( 1 L / 1000 mL )
Molarity = 0.07 M
Hope this answers the question. Have a nice day.</span>
Answer:
b. Cu(OH)2
Explanation:
As it is having Hydroxil ions(OH).
The number of electrons that can occupy the sub levels being filled by that period