the thallium nucleus is radioactive, with a half-life of approximately 3.0 min. at a given instant, the activity of a certain sample of thallium is 2400 bq. using the concept of half-life, what is the approximate activity of the sample 9 minutes later?

Turbo the snail moves across the ground at a pace of 12 feet per day. if the garden is 48 feet away, how many days will it take for the snail to get there?

Asolution contains 180 g of glucose (c6h12o6) and 162 g of water. what is the mole fraction of glucose?

Nebulae are enormous clouds in outer space. they are made mostly of hydrogen gas, helium gas, and dust. some nebulae glow brightly, while others do not. the stars that people see are huge, bright balls of glowing gas. they are made mostly of hydrogen and helium. which statement correctly describes other ways in which nebulae and stars are different? a. stars can form inside a nebula but a nebula can never be produced by any star. b. a star always has a higher density than a nebula. c. stars can never form inside a nebula but a nebula can be produced by any star. d. a nebula always has a higher density than a star.