Suppose you have 50 grams of a radioactive isotope with a half-life of 2 years. how much of the isotope will you have after 4 years?
a) 50
b) 25
c) 12.5

If 1.63 times 10 negative 4 of helium dissolves in 100.0g of water, what is the concentration in parts per million

Select the correct text in the passage. which sentences describe examples of sustainable living? i live in an old apartment building downtown, but my company is based in an office park on the outskirts of the city. i drive an old car that needs to be replaced. i plan to buy a hybrid for better gas mileage, but for now i am able to carpool with a couple of friends from work. the drive to the office park is about 45 minutes each way, but we do get to work in a modern building. the architects just received a leed certification for the design.

How have the greenhouse gasses increased from the year 2000 to 2018