3) 39.10g/65.10times 100% 12.01/65.10gtimes 100% K __ C __ N: __ disappointed 14.01/65.10times 100% 4) PI_(3) P: __ I: __

3) To calculate the percentage composition of each element in the compound, we need to divide the mass of each element by the total mass of the compound and then multiply by 100%.<br /><br />For the first expression:<br />$39.10g/65.10\times 100\% = 60.00\%$<br /><br />For the second expression:<br />$12.01/65.10g\times 100\% = 18.45\%$<br /><br />For the third expression:<br />$14.01/65.10\times 100\% = 21.55\%$<br /><br />So, the percentage composition of each element is:<br />K: 60.00%<br />C: 18.45%<br />N: 21.55%<br /><br />4) In the compound $PI_{3}$, the elements present are:<br />P: 1 atom<br />I: 3 atoms<br /><br />Therefore, the percentage composition of each element is:<br />P: 100%<br />I: 100%