Answer
1.4
Work Step by Step
Let's say that the balloon originally contained 1 mole of both H2 and O2. If 35% of the H2 leaked out, then the remaining amount of H2 would be 0.65 moles. If the O2 leaks out at 1/4 of the H2 rate, then
1/4 x 35% = 8.8% of the O2 leaked out. that would leave 0.912 moles of O2 in the balloon.
The new O2/H2 mole ratio is 0.912 / 0.65 = 1.4
