It will be 1.247 rods that will equal 247 inches.
1. Convert the number of moles to number of particles (divide 6.41 by 6.022 x 10^23)
2. K2O dissociates into three ions (2 potassium ions and 1 oxide ion), so multiply the result from step 1 by 3 to get your answer
Chlorine has a charge -1. It means that X is +2 so that the formula is XCl2. Group 2 is the correct answer.