Question

How many moles of O2 are needed to react with 0.56 moles of K?

Answer 1

assuming the reaction is:
\[4K+O_2 \rightarrow 2K_2O\]
then if the number of moles of K is 0.56, the number of moles of O2 should be 1/4 of it, hence 0.14 mol