If two half lives have passed since a scientist collected a 1.00- gram sample of a U-235, how much U-235 is left now? answers for most finals chem test questions (10th)

Liquid from a brewery fermentation contains 10% ethanol and 90% water. part of the fermentation product (50,000 kg/h) is pumped to a distillation column on the factory site. under current operating conditions, a distillate of 45% ethanol and 55% water is produced from the top of the column at a rate of one-tenth that of the feed. what is the composition of the waste "bottoms" from the still?