A gas with a volume of 4.2L at 0.610atm is allowed to expand until the pressure drops to 0.25atm. What will be the new volume?

The answer for #3 is c but i don't know why

Consider the nuclear equation below. 239 > x + 4 he 94 2 what is x? 1.235 cm 96 2.243 u 92 3.235 u 92 4.243 cm 96

Consider the reduction reactions and their equilibrium constants. cu+(aq)+e−↽−−⇀cu(s)pb2+(aq)+2e−↽−−⇀pb(s)fe3+(aq)+3e−↽−−⇀fe(=6.2×108=4.0×10−5=9.3×10−3 cu + ( aq ) + e − ↽ − − ⇀ cu ( s ) k =6.2× 10 8 pb 2 + ( aq ) +2 e − ↽ − − ⇀ pb ( s ) k =4.0× 10 − 5 fe 3 + ( aq ) +3 e − ↽ − − ⇀ fe ( s ) k =9.3× 10 − 3 arrange these ions from strongest to weakest oxidizing agent.