An 80.0 g sample of iodine-131 was placed in a sealed vessel forty days ago. Only 2.5 g of this isotope is now left. What is its half-life?

26. (a) Calculate the number of atoms in 64g of oxygen gas. [O=16] (b) Which has a greater number of atoms 10g of hydrogen gas or 10g of helium gas? [H=1; He=4] (c) Calculate the mass of 0.5 mole of oxygen gas. [O=16] (d) Calculate the mass of 3.

What is the primary type of energy conversion that takes place inside a battery-powered phone when it is turned on? O A. Light energy to electrical energy O B. Chemical energy to electrical energy O c. Chemical energy to light energy O D.

How did scientist account for fossils and other geological evidence as they developed the geologic time scale

Explain how the atomic theory was modified from Dalton's theory to Rutherford's. Include an explanation of why the theory was modified.

Find the element that has the same chemical properties as magnesium, but fewer protons

If you see the Sun is high in the sky, what can you say about the SUN as viewed from the opposite side of Earth at the same moment?

What element has 8 valence electrons

Which of the following best describes a metal? Brittle, shiny, and solid Brittle, dull, and low density Malleable, shiny, and able to conduct heat or electricity Malleable, dull, and solid, liquid, or gas at room temperature?

Which of the following errors could cause your percent yield to be falsely high, or even over 100%? Select ALL that apply. A.) Heating the sample too vigorously. B.) Handling the crucible directly with your hands. C.

If 56.8 ml of bacl2 solution is needed to precipitate all the sulfate ion in a 554 mg sample of na2so4 (forming baso4), what is the molarity of the solution?