You are on the right track! To determine the number of grams of iodine in another sample containing 9.56 g of potassium, you will need to use the information from the initial sample.
First, let's find the ratio of potassium to iodine in the initial sample. Since the compound contains only potassium and iodine, the remaining mass must be iodine. Therefore, we can calculate the mass of iodine in the initial sample by subtracting the mass of potassium from the total mass of the compound:
Mass of iodine = Total mass of compound - Mass of potassium
Mass of iodine = 12.3 g - 2.90 g
Now we can find the ratio of potassium to iodine by dividing the mass of potassium by the mass of iodine in the initial sample:
Ratio of potassium to iodine = Mass of potassium / Mass of iodine
Ratio of potassium to iodine = 2.90 g / (12.3 g - 2.90 g)
Next, we can use this ratio to calculate the mass of iodine in the sample containing 9.56 g of potassium. We can set up a proportion using the known ratio:
(Mass of iodine in second sample) / 9.56 g = (Mass of iodine in initial sample) / 2.90 g
To solve for the mass of iodine in the second sample, we can cross-multiply and divide:
Mass of iodine in second sample = (Mass of iodine in initial sample / 2.90 g) * 9.56 g
Now you can plug the values into the equation and calculate the mass of iodine in the second sample.