Answer:
60 moles of NaF
Explanation:
The balanced equation for the reaction is given below:
Al(NO3)3 + 3NaF —> 3NaNO3 + AlF3
From the balanced equation above,
3 moles of NaF reacted to produce 1 mole of AlF3.
Therefore, Xmol of NaF will react to produce 20 moles of AlF3 i.e
Xmol of NaF = 3 x 20
Xmol of NaF = 60 moles
Therefore, 60 moles of NaF are required to produce 20 moles of AlF3.
Answer:
Specific Rotation = 105º
S% in mixture = 92%
Explanation:
Specific rotation in organic compounds varies linearly, then the enantiomeric excess can be express as:

Where alpha is the specific rotation of the mixture and alpha pure is the specific rotation of the excess enantiomer.
Then, knowing that the S enantiomer is in excess you can calculate the specific rotation of that mixture:


For calculating the percentage of S you should remember that the enantiometric excess is the percentage of excess of a certain enantiomer, for example in this case:

Since S is in Excess
Also, it is true:

Then you can solve the system of linear equations, finding:

Hope it helps!
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