Which atmosphere layer contains electrically changed particles that reflect radio waves?

What is the molarity of 1.5 liters of an aqueous solution that contains 52 grams of lithium fluoride, LiF, (gram-formula mass = 26 grams/mole) ? (1) 1.3 M (3) 3.0 M (2) 2.0 M (4) 0.75 M

The atomic mass of hydrogen-1 is 1.008 and the atomic mass of helium-4 is 4.003. Find the difference in grams between 4 moles of hydrogen and one mole of helium. A) 4.81 x10-26 g B) 0.029 g C) 1.7 x 1022 g D) 0 grams

Light travels extremely rapidly (c = 3.00*108 m/s). Suppose you had to travel 40 miles to work every day. If you traveled at the speed of light for the entire trip, how long would it take you to get to work (in seconds) ? [1 mile = 1.61 km]

What group of elements are the most chemically reactive?

Which nuclide is most likely to be radioactive and synthetic?

If 6 moles of a compound produce 84 J of energy, what is the a Hreaction in J/mol?

If you were traveling through space and landed on a different planet, how might your mass and weight compare to their values on Earth? Why?

Which principle explains why it is necessary to have safety belts in cars?

Hydrochloric acid is purchased in 12 molar concentrations. If I needed 200 ml of 2.0 molar HCl, how many milliliters of the concentrated solution would I need

Which of the following represents a chemical change? Bending a wire Freezing of water Fireworks exploding Melting of a wax candle