#### Answer

Because the ratio (5:3) consists of small whole numbers, the results are consistent with the law of proportions.

#### Work Step by Step

1: Recognize the law of proportions states if two elements combine to form two (or more) compounds, the ratio of masses of one element that combines with the fixed elements mass is expressed in small whole numbers.
2. Therefore, we place the mass of phosphorus to the mass of chlorine, for the first compound in the numerator, then place the ratio of the mass of phosphorus to the mass of chlorine for the second compound in the denominator. This is simplified and written in ratio form.
1:(mass P)/(mass Cl)=0.2912 g P/ 1 g Cl
2: (mass P)/ (mass Cl)= 0.1747 g P/ 1 g Cl
Simplify: =1.667=5/3=5:3 (This is a ratio of small whole numbers and therefore is consistent to the law of proportions).