Explanation:
The given compounds are oxyacids and in these compounds more is the electronegativity of the central atom more will be its acidic strength.
This is because more is the electronegativity of the central atom more will be the polarity of OH bond. As a result, the compound can readily lose 
ion.
Also, more is the electronegativity of central atom more will be the stability of conjugate base formed.
Thus, we can conclude that given compounds are arranged in increasing acid strength as follows.
HOI < 
< 
< HOF
Unfortunately the data provided doesn't include the DENSITY of the ammonium chloride solution and molarity is defined as moles per volume. So without the density, the calculation of the molarity is impossible. But fortunately, there are tables available that do provide the required density and for a 20% solution by weight, the density of the solution is 1.057 g/ml.
So 1 liter of solution will mass 1057 grams and the mass of ammonium chloride will be 0.2 * 1057 g = 211.4 g. The number of moles will then be 211.4 g / 53.5 g/mol = 3.951401869 mol. Rounding to 3 significant digits gives a molarity of 3.95.
Now assuming that your teacher wants you to assume that the solution masses 1.00 g/ml, then the mass of ammonium chloride will only be 200g, and that is only (200/53.5) = 3.74 moles.
So in conclusion, the expected answer is 3.74 M, although the correct answer using missing information is 3.95 M.
Answer:
Heating the liquids and letting one boil away first :)
Explanation:
