Answer
$R_3Q$
Work Step by Step
By the law of multiple proportions, we find the following ratios of elements of R to 1 gram of Q for both compounds:
Compound 1: 14.0/3.0=4.67 grams of R per 1 gram of Q
Compound 2: 7.00/4.50=1.56 grams of R per 1 gram of Q
The ratio of these two values is 3. Therefore, if the formula of the second compound is $RQ$, because there is three times more R per gram of Q in the first compound, the formula of the first compound would be $R_3Q$ by the law of multiple proportions.
