A 0.80-kg soccer ball experinces an impulse of 25 N x s . Determine the momentum change of the soccer ball.

If the impulse is 25 N-s, then so is the change in momentum. The mass of the ball is extra, unneeded information.Just to make sure, we can check out the units:Momentum = (mass) x (speed) = kg-meter / secImpulse = (force) x (time) = (kg-meter / sec²) x (sec) = kg-meter / sec 

I don't know if this question is worded incorrectly, but impulse is, by definition, the change in momentum. Thus, the change in momentum is 25 N*s.