To solve this problem we must first find the masses of each individual compound. Then we can use the following equation:
(mass of strontium) / (mass of compound) * 100% = (percent mass of Strontium)
1. The mass of strontium is 87.62 and the mass of Chlorine is 35.45. There are 2 chlorine atoms in the compound, so 35.45*2 = 70.9. Add the strontium to get the mass of compound. 70.9 + 87.62 = 158.52. Now, we can use the equation.
87.62 / 158.52 * 100% = 55.27% Strontium
2. There are 2 Iodine atoms in the compound, and the molar mass of Iodine is 126.9. The mass of the compound is 126.9 + 87.62 = 214.52. Now, we can use the equation
87.62 / 214.52 * 100% = 40.84% Strontium
3. The molar mass of Oxygen is 16, and there is only one oxygen atom. So the mass of the compound will be 16 + 87.62 = 103.62. Now we can use the equation.
87.62 / 103.62 * 100% = 85.46% Strontium
4. Finally, the molar mass of sulfur is 32.06, and there is only one sulfur atom in the compound, so the mass will be 32.06 + 87.62 = 119.68. Now we can use the equation
87.62 / 119.68 * 100% = 73.21% Strontium
Therefore, the answer is 3 because it has the highest percentage of Strontium than the other compounds. Hope this helped!! :D