D. all of the above, although I do find it hard to believe something like flour would have a melting point, I looked up my answer to double check.
17) 8.4 / 20 x 100
18) 20 . 0.5150
19) 6,50% because (as you said) the law of definite proportions states that regardless of the amount, a compound is always composed of the same elements in the same proportion by mass
Acetic acid is 60.05 grams/mole. In 1 liter of vinegar or 1000 ml there would be 0.046% of acetic acid = 46 ml x 1.005g/ml = 46.23 grams/60.05 grams= 0.77 moles per litre of vinegar.This then would be the concentration of acetic acid in for example 1 liter of vinegar.
