Which one of these statements is correct?
The mole ratio of the cation and the anion in a precipitate is an integer.
The mole ratio of the cation and the anion in a precipitate is a simple fraction.
The mole ratio of the cation and the anion in a precipitate can be any number.
The correct answer is the second statement. The molar ratio of the anion and cation in a precipitate is a simple fraction. The molar ratio can be an integer but it will not always be. For the ratio to be an integer, one of the components of the ratio must be a 1. This is true for something like AgCl which has a molar ratio of 1:1 which becomes 1 in fraction form. But for Al2S3, the molar ratio is 2:3 which does not give an integer in fraction form but a simple fraction instead. Finally, the ratios cannot be any number because ions can only join together to form compounds in whole number ratios (no decimals). So the second statement is the correct answer.