<u>Answer:</u> Osmolarity of the sodium chloride solution is 18 Osmol/L.
<u>Explanation:</u>
Osmolarity is defined as the the concentration of the solution which is expressed as the total number of solution particles present in one liter of solvent.
We are given the molarity of the solution which is 3mol/L and to convert it into osmolarity, we will multiply the number of osmoles that are produced by the solute.
Osmole is defined as the particles that contribute to the osmotic pressure of a solution.
The solute given here is sodium chloride (NaCl). Number of osmoles can be determined by the dissociation of this solvent into ions.
The equation given by the dissociation of NaCl:

1 mole of sodium chloride produces 2 moles of ions.
So, 3 moles of sodium chloride will produce = (3 × 2) = 6 moles of ions.
Hence, osmolarity of the sodium chloride solution will be 
Answer:
15.98 L
Explanation:
First, you need to find T1, T2, V1 and V2.
T1 = 25 C = 298.15 K (25C + 273.15K)
T2 = 100 C = 373.15 K (100C + 273.15K)
V1 = 20. L
V2 = ? (we are trying to find)
Next, rearrange to fit the formula
V2 = V1 x T1 / T2
Next, fill in with our numbers
V2 = 20. L x 298.15 K / 373.15 K
Do the math and you should get...
15.98 L
- If you need more help or futher explanation please let me know. I would be glad to help!
To do this problem it is necessary to take into account that the heat given by the unknown substance is equal to the heat absorbed by the water, but considering the correct sign:

Clearing the specific heat of the unknown substance:

The first one is Solid, or A.
The second: B or liquids.
Third: also B I think.
Hope this helps.