<span>Molar mass of chloroform (CHCl3)
C = 1 * 12 = 12 a.m.u
H = 1 * 1 = 1 a.m.u
Cl = 3 * 35.5 = 106.5 a.m.u
Molar Mass (CHCl3) = 12 + 1 + 106.5 = 119.5 g / mol
Knowing that:
The value of Avogadro's constant corresponds to approximately </span>

molecules, if chloroform contains

molecules. <span>
We have:
</span>

<span>
Now, how many grams are there in the chloroform molecule?
grams -------- molecules</span><span>
119,5 </span>→

x →




Answer:
- <u><em>He must use 50g of the 12% solution and 30 g of the 20% solution.</em></u>
<u><em></em></u>
Explanation:
Call x the amount of <em>12% boric acid </em>solution to be used.
- The content of acid of that is: 0.12x
Since he wants to make <em>80 grams</em> of solution, the amount of <em>20% boric acid</em> solution to be used is 80 - x.
- The content of acid of that is{ 0.20(80 - x).
The final solution is <em>15% </em>concentrated.
- The content of boric acid of that is 0.15 × 80 g.
Now you have can write your equation:

Solve:

That is 50 grams of the 12% solution of boric acid.
Calculate the amount of the 20% solution of boric acid:

That is 30 grams.
Then, he must use 50g of the 12% solution and 30 g of the 20% solution.
Answer: 1.14mol
Nitrogen molar mass=14g/mol
N2 molar mass=14*2=28g/mol
31.9g(1/28)=1.14mol N2